feat(pihole): declare the admin password and adlists in git

Prerequisite for running more than one PiHole replica. A second replica with a
fresh PVC would have come up serving DNS and blocking nothing, with a different
admin password -- answers varying by which pod replied.

pihole.toml's own ### CHANGED markers gave the exact inventory: four settings
already came from env (declared), one came from the image, and exactly ONE
operator-set value lived only on the PVC -- webserver.api.pwhash, a one-way hash
nobody could recover. Separately the adlists were undeclared: one list and 72,234
gravity domains that nothing in this repo named.

Declares both:
- A SOPS secret feeding FTLCONF_webserver_api_password. webserver.api.password
  takes cleartext and FTL hashes it itself (verified: pihole setpassword IS
  setFTLConfigValue on that key), so the PVC's pwhash becomes derived state.
- A level-triggered postStart hook that reconciles the declared adlist set into
  gravity.db -- adds, re-enables, and disables (never deletes) undeclared lists,
  running pihole -g only when something moved. A file would not work: v6's
  adlists.list import is migration-only, guarded on the DB not existing.

The rendered hook was run in the live pod against throwaway copies of gravity.db,
exercising all four paths. A fresh DB built from the image's own schema template
has ZERO adlists, confirming this is load-bearing rather than cosmetic.

Password kept rather than set empty: the pihole Service still publishes port 80
past the oauth2-proxy, closed only by policy, and default-deny has drifted here
before.

Multi-replica is phase 2 and deliberately not in this branch -- it needs a schema
field, a StatefulSet (the config PVC is RWO), anti-affinity and a PDB.

Adds a *.sops.yaml -- a sensitive path -- so approval-policy will block pending
an operator /approve-override.

Co-Authored-By: Claude Opus 5 (1M context) <[email protected]>

catalog/pihole.yaml

@@ -100,6 +100,20 @@ env:
   # while resolution for the zone does not work. Confirmed both ways against the live image.
   - name: FTLCONF_misc_dnsmasq_lines
     value: "address=/${BASE_DOMAIN}/${GATEWAY_VIP};address=/unifi.${BASE_DOMAIN}/${UNIFI_L4_VIP};address=/crafty-mc.${BASE_DOMAIN}/${CRAFTY_L4_VIP};address=/pihole-dns.${BASE_DOMAIN}/${PIHOLE_DNS_VIP}"
+  # THE ADMIN PASSWORD, previously the ONE operator-set value declared nowhere. Sourced from
+  # apps/wave-0/pihole-bootstrap-secret.sops.yaml (SOPS/age, same wave => same reconcile), which
+  # carries the full rationale and the measurement that found it.
+  #
+  # `webserver.api.password` takes CLEARTEXT and FTL hashes it itself into `webserver.api.pwhash`.
+  # Verified in the running image, not assumed: `pihole setpassword` is itself
+  # `setFTLConfigValue "webserver.api.password" "$PASSWORD"`, commented upstream as "pihole-FTL will
+  # automatically hash the password". So the BALLOON-SHA256 hash on the PVC is now a DERIVED artefact
+  # and this is its source of truth. Rotating the Secret rotates the password.
+  - name: FTLCONF_webserver_api_password
+    valueFrom:
+      secretKeyRef:
+        name: pihole-bootstrap
+        key: webui-password
 ingressRoutes:
   - host: pihole.${BASE_DOMAIN}
     port: 80                  # admin web UI, protected at the Gateway by forward-auth (docs/09)
@@ -114,6 +128,110 @@ auth:
   # rather than a renderer constant: the measurement that justifies the flag on two apps is
   # evidence about those two apps. Its oauth2-proxy log holds 0 unauthenticated requests across
   # the current pod's whole 23h lifetime (measured 2026-10-01), so there is nothing to act on.
+lifecycle:
+  # LEVEL-TRIGGERED ADLIST ASSERTION, run on EVERY container start. Same pattern, and the same
+  # reasoning, as catalog/qbittorrent.yaml's postStart: desired state lives in git and is
+  # RE-ASSERTED unconditionally rather than set once by hand.
+  #
+  # WHY THIS IS NEEDED AT ALL — the blocklists were NOT reproducible from git. Measured on live prod
+  # 2026-10-04: `gravity.db` held exactly ONE adlist (StevenBlack's hosts, enabled) and 72,234
+  # gravity domains, and NOTHING in this repo named it. Worse, a FRESH database does not seed it:
+  # the image's own schema template `/etc/.pihole/advanced/Templates/gravity.db.sql` creates the
+  # `adlist` table and inserts NO rows into it (grepped in the running image — there is no
+  # `INSERT INTO adlist` at all). So a rebuild from git, or a replica with a new PVC, would come up
+  # SERVING DNS AND BLOCKING NOTHING, silently and with every object reporting healthy.
+  #
+  # WHY A postStart HOOK AND NOT A FILE. PiHole v6 keeps adlists as DB rows, not config. The
+  # `/etc/pihole/adlists.list` file still exists in `gravity.sh` but is MIGRATION-ONLY: its import
+  # sits inside `migrate_to_database()`, guarded by `if [ ! -e "$gravityDBfile" ]`, so it fires only
+  # while CREATING a database and never again on an existing one. A ConfigMap mounted there would
+  # therefore be silently ignored on every pod this cluster currently runs. There is also no
+  # `pihole adlist` CLI subcommand (only allow/deny for domains), so SQL against the DB is the
+  # actual interface. FTL ships an embedded shell (`pihole-FTL sqlite3`, SQLite 3.53.1) so no extra
+  # tooling is needed in the image.
+  #
+  # IT RECONCILES, IT DOES NOT JUST ADD: adlists present in the DB but absent from DECLARED below are
+  # DISABLED (not deleted — deleting cascades to `gravity` rows and would force a full re-download of
+  # everything on a typo). So this list is the source of truth in both directions, and `pihole -g`
+  # runs ONLY when something actually changed, which keeps the steady-state start free of a 70k-domain
+  # rebuild.
+  #
+  # NO BRACED DOLLAR EXPANSION ANYWHERE IN THIS SCRIPT, DELIBERATELY — the same contract
+  # catalog/qbittorrent.yaml documents at length. apps-wave-0 declares postBuild.substituteFrom
+  # cluster-vars, so Flux runs envsubst over this whole manifest at reconcile time; a `${VAR}` form
+  # would behave differently on the cluster than under a plain `kubectl apply` of the golden. Bare
+  # `$VAR` and `$(cmd)` are untouched by envsubst and so behave identically however this is run.
+  # `render.py`'s assert_substitution_safe refuses to emit a manifest that breaks this.
+  postStart:
+    exec:
+      command:
+        - /bin/bash
+        - -c
+        - |
+          # Assert the declared adlists in gravity.db. Idempotent: steady state writes nothing and
+          # does NOT run a gravity rebuild.
+          set -u
+          GRAVITY=/etc/pihole/gravity.db
+
+          # THE DECLARED SET — one URL per line, the source of truth for what PiHole blocks.
+          # To add a list: add a line here, commit, let Flux reconcile. Nothing else to do.
+          DECLARED='https://raw.githubusercontent.com/StevenBlack/hosts/master/hosts'
+
+          # On a fresh PVC, FTL creates gravity.db a moment after the container starts. Wait, bounded,
+          # and NEVER block or fail the start: a missing DB here must not crashloop DNS for the LAN.
+          i=0
+          while [ ! -s "$GRAVITY" ] && [ "$i" -lt 90 ]; do sleep 2; i=$(expr $i + 1); done
+          if [ ! -s "$GRAVITY" ]; then
+            echo "pihole-adlists: gravity.db absent after 180s - leaving adlists untouched" >&2
+            exit 0
+          fi
+
+          sql() { pihole-FTL sqlite3 "$GRAVITY" "$1"; }
+          CHANGED=0
+
+          # 1) Every declared URL must be present AND enabled.
+          echo "$DECLARED" | while IFS= read -r url; do
+            [ -n "$url" ] || continue
+            printf '%s\n' "$url"
+          done > /tmp/declared.txt
+          while IFS= read -r url; do
+            [ -n "$url" ] || continue
+            # Single quotes inside a URL would break this SQL; adlist URLs do not contain them.
+            have=$(sql "select count(*) from adlist where address='$url';")
+            if [ "$have" = "0" ]; then
+              echo "pihole-adlists: adding $url"
+              sql "insert into adlist (address,enabled,comment) values ('$url',1,'declared in catalog/pihole.yaml');"
+              CHANGED=1
+            else
+              en=$(sql "select enabled from adlist where address='$url';")
+              if [ "$en" != "1" ]; then
+                echo "pihole-adlists: re-enabling $url"
+                sql "update adlist set enabled=1 where address='$url';"
+                CHANGED=1
+              fi
+            fi
+          done < /tmp/declared.txt
+
+          # 2) Anything enabled in the DB but NOT declared gets disabled (never deleted - see above).
+          sql "select address from adlist where enabled=1;" | while IFS= read -r addr; do
+            [ -n "$addr" ] || continue
+            if ! grep -qxF "$addr" /tmp/declared.txt; then
+              echo "pihole-adlists: disabling undeclared $addr"
+              sql "update adlist set enabled=0 where address='$addr';"
+              echo changed >> /tmp/adlist-changed
+            fi
+          done
+          [ -s /tmp/adlist-changed ] && CHANGED=1
+          rm -f /tmp/adlist-changed /tmp/declared.txt
+
+          # 3) Rebuild gravity ONLY if the declared set actually moved.
+          if [ "$CHANGED" = "1" ]; then
+            echo "pihole-adlists: declared set changed - running gravity update"
+            pihole -g || echo "pihole-adlists: gravity update failed; existing gravity.db retained" >&2
+          else
+            echo "pihole-adlists: already matches the declared set - nothing to do"
+          fi
+          exit 0
 update:
   channel: stable             # R-UPD-01
   range: ">=2024.0.0"