feat(gitea): upgrade 1.27.3 -> 28.3.0

Gitea dropped the "1." prefix; 28.x is the successor of 1.27.
- image 28.3.0, update.range >=28.0.0 <29.0.0, Renovate ceiling <29.0.0
- drop GITEA__server__DOMAIN (no longer read in 28, ROOT_URL is the source)
- declare RUN_RETENTION_DAYS=400, EGRESS_MODE=lax (no allow list: the OIDC
  login source is not gated by the egress policy in 28.3.0), and
  DISABLE_REGISTRATION=true (28's new default)
- document autoRollbackOnFailedHealth as inert (no ImagePolicy is rendered);
  rollback is a PVC restore because the DB migration is one-way

Co-Authored-By: Claude Opus 5.5 <[email protected]>

decisions/2026-11-07-gitea-28.md

@@ -0,0 +1,62 @@
+---
+date: 2026-11-07
+branch: feat/gitea-28
+title: "Gitea 1.27.3 -> 28.3.0 (upstream dropped the 1. prefix)"
+---
+
+## What changed
+
+- `catalog/gitea.yaml`: `source.image` `gitea/gitea:1.27.3` -> `gitea/gitea:28.3.0` (still the
+  newest stable tag on Docker Hub and GitHub on 2026-11-07: 28.0.0, 28.1.0, 28.2.0, 28.3.0).
+  `update.range` `">=1.22.0 <2.0.0"` -> `">=28.0.0 <29.0.0"`.
+- 28.x breaking changes handled in the env block:
+  - `GITEA__server__DOMAIN` **removed**: 28 no longer reads `[server] DOMAIN` (go-gitea/gitea#39400);
+    `ROOT_URL` was already set and is now the only source of the domain. Nothing else in the repo
+    reads the variable (the bootstrap script sets ROOT_URL/SSH_PORT only).
+  - `GITEA__actions__RUN_RETENTION_DAYS=400` **declared** (go-gitea/gitea#38855 added the 400-day
+    default; the spec repo states no CI-history retention requirement).
+  - `GITEA__security__EGRESS_MODE=lax` **declared, with no allow list.** Read from the 28.3.0
+    source: the Keycloak OIDC login source does NOT go through the new egress policy (goth's
+    openidConnect provider, default HTTP client). The policy covers webhooks, the OAuth2 avatar
+    fetch (`UPDATE_AVATAR` is off) and OpenID 2.0. A hostname entry would not even help for a
+    private address — `WithLocalNeedsIPAllow` requires an IP/CIDR entry. So the brief's
+    "Keycloak SSO breaks" premise does not hold for 28.3.0, and an allow-list entry would only
+    widen webhook SSRF reach.
+  - `GITEA__service__DISABLE_REGISTRATION=true` **declared** (28's new default; 1.27 defaulted it
+    open). OAuth2 auto-registration is gated separately and keeps working.
+- `update.autoRollbackOnFailedHealth`: kept `true`, commented as **inert**. It renders only an
+  annotation on a Flux ImagePolicy, and `apps/` is rendered `--no-image-automation`, so no
+  ImagePolicy exists. The Deployment is `Recreate` with no probes, so nothing reverts the image
+  automatically. Rollback = restore the PVC, never an image revert onto the migrated DB.
+- `apps/wave-0/gitea.yaml` re-rendered with the canonical command
+  (`render.py --all catalog -o apps --wave-layout --no-image-automation`, in the toolbox). Only
+  gitea changed.
+- `renovate.json5`: gitea `allowedVersions` `<2.0.0` -> `<29.0.0`; the description no longer calls
+  28.x a stale tag.
+
+## What I verified
+
+- Docker Hub tag list and GitHub tags: 28.3.0 is the newest 28.x stable tag.
+- Read the v28.3.0 source: `modules/egress/policy/policy.go`, `modules/egress/policies.go`, every
+  `egress.New*` caller, `services/auth/source/oauth2/providers_openid.go`,
+  `modules/setting/{security,actions,service}.go`, `routers/web/auth/{oauth,linkaccount}.go`,
+  `cmd/admin_user_list.go`, `cmd/admin_auth*.go`, the Dockerfile, and `docker/root` (the s6 setup
+  still runs `environment-to-ini`). The postStart hook's CLI is unchanged in 28.3.0: `admin user
+  list --admin` still has Username in column 2, `admin auth list` still has ID/Name in columns 1/2,
+  `add-oauth`/`update-oauth` keep the same flags, and curl and su-exec are still in the image.
+- Live Gitea (API, 2026-11-07): version 1.27.3. Zero repo, org and system webhooks, no mirrors.
+- `renovate-config-validator` at 44.167.0 (the tag renovate.yaml pins): "Config validated
+  successfully".
+- Ran the toolbox gate on the committed tree (numbers are in the PR).
+
+## What I did NOT verify
+
+- **The upgrade itself.** Nothing booted 28.3.0 against a copy of the production DB. Migration
+  time, migration success and the post-upgrade SSO login are all UNVERIFIED, and the PR's
+  post-merge checklist covers them.
+- **The age of the latest gitea-data Longhorn/off-cluster backup.** The cluster read failed from
+  the worktree (no k3s-prod context with the kubeconfig available), so the operator must confirm
+  it before merging.
+- How the Envoy Gateway handles the new `/-/ws` WebSocket. If upgrades are not forwarded, live
+  notifications fall back to polling (not breaking). UNVERIFIED.
+- Whether the L2/L3 conformance suite passes. It does not run in CI.