feat(gitea): update Helm values with external DB/cache config and add SOPS policy

Restores the newer local gitea-values.sops.yaml (2026-03-27) over the
upstream scaffold (2026-03-10). Adds database, cache, session, and queue
sections pointing to external PostgreSQL/Valkey (S3 platform services),
and disables bundled postgresql/redis/valkey sub-charts.

Also adds .sops.yaml encryption policy for railiance-apps.

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

.sops.yaml

@@ -0,0 +1,8 @@
+# SOPS encryption policy for railiance-apps
+# Encrypts any file matching *.sops.yaml using the shared age key.
+
+creation_rules:
+  - path_regex: \.sops\.yaml$
+    key_groups:
+      - age:
+          - age1aq8twfd78wvpra0had8cezcnj96tj4q0068edrz5jez8d6xwmflqdepsh4