fix(vpn): correct env name PRIVATE_INTERNET_ACCESS_OPENVPN_ENCRYPTION_PRESET

gluetun silently ignored PIA_ENCRYPTION_PRESET (renamed) and defaulted to strong
(RSA-4096) the whole time. The correct v3.x var is
PRIVATE_INTERNET_ACCESS_OPENVPN_ENCRYPTION_PRESET=normal → RSA-2048/AES-128-CBC/1198,
the smaller handshake that fits the 1450 pod MTU.

Co-Authored-By: Claude Opus 4.8 <[email protected]>

platform/vpn-egress/gluetun-gateway.yaml

@@ -53,7 +53,7 @@ spec:
               value: "private internet access"
             - name: VPN_TYPE
               value: "openvpn"               # OpenVPN-UDP — satisfies "protocol != TCP" (R-NET); ADR-0013 amended
-            - name: PIA_ENCRYPTION_PRESET
+            - name: PRIVATE_INTERNET_ACCESS_OPENVPN_ENCRYPTION_PRESET
               value: "normal"                # PIA "normal": RSA-2048 + AES-128-CBC + SHA1, port 1198 (matches the
                                              # operator's downloaded lower-encryption .ovpn). Chosen over "strong"
                                              # (RSA-4096): the smaller handshake fits the pod's 1450 MTU (Cilium