chore(ci): migrate workflows to gitea + consolidate keystore secret

- rename .forgejo/workflows/ to .gitea/workflows/ (git mv preserves
  history); Gitea Actions reads either path, but the directory now
  matches the active platform
- collapse ANDROID_STORE_PASSWORD + ANDROID_KEY_PASSWORD into a
  single ANDROID_KEYSTORE_PASSWORD secret (PKCS12 keystores require
  the two passwords to be identical, so the duplication carried no
  information); build.gradle.kts still reads two env vars to stay
  format-agnostic, both now sourced from the same secret in CI
- ignore android/*.keystore, android/*.keystore.*, android/*.jks,
  android/keystore.properties so the regenerated signing material
  never reaches a remote on accident
- update prose references from Forgejo to Gitea in CLAUDE.md and
  the docs; the historical "migrated from Forgejo" note in CLAUDE.md
  is kept intentionally; forgejo/upload-artifact@v3 action refs are
  left untouched (canonical artifact action, resolves cleanly under
  Gitea Actions)

Operator side: ANDROID_KEY_ALIAS, ANDROID_KEYSTORE_PASSWORD, and
ANDROID_KEYSTORE_B64 secrets registered in Gitea before this lands.

ci-requirements.md

@@ -12,8 +12,8 @@ git.fabledsword.com/bvandeusen/ci-go:1.26
 git.fabledsword.com/bvandeusen/ci-flutter:3.44
 ```
 
-- `ci-go:1.26` — Go server tests (`.forgejo/workflows/test-go.yml`), web SPA tests (`.forgejo/workflows/test-web.yml`), and the release container build (`.forgejo/workflows/release.yml`).
-- `ci-flutter:3.44` — Flutter client tests + debug/release APK builds (`.forgejo/workflows/flutter.yml`).
+- `ci-go:1.26` — Go server tests (`.gitea/workflows/test-go.yml`), web SPA tests (`.gitea/workflows/test-web.yml`), and the release container build (`.gitea/workflows/release.yml`).
+- `ci-flutter:3.44` — Flutter client tests + debug/release APK builds (`.gitea/workflows/flutter.yml`).
 
 ## Image deps used
 
@@ -42,6 +42,6 @@ None.
 - **Label/image split.** Workflows keep `runs-on: go-ci` / `runs-on: flutter-ci` as the scheduling label per the [`ci-runners.md`](https://…/FabledRulebook/ci-runners.md) "label = scheduling handle, image = `container.image`" pattern. The labels are intentional handles, not toolchain assertions.
 - **Integration-job docker-socket dependency.** `test-go.yml`'s integration job uses the runner's shared docker socket (`/var/run/docker.sock`) to bridge-IP-discover the per-job Postgres service container by name + network intersection — the dev compose's `minstrel-postgres-*` containers are explicitly skipped as belt-and-suspenders. Depends on `act_runner.valid_volumes` whitelisting the socket; if that ever stops auto-mounting, integration tests fail at the `docker inspect` step.
 - **Go toolchain pin.** `go.mod` is on `go 1.25.0` because `golang.org/x/crypto v0.51.0` declares 1.25 as its minimum. `ci-go:1.26` satisfies this with headroom. Future `x/crypto` bumps that move the Go floor should be paired with an image-tag bump in this file + the workflows.
-- **In-app update channel polling.** `release.yml` polls Forgejo's release-asset API for up to 15 min on tag pushes to fetch the APK that `flutter.yml` is concurrently attaching to the same release. The asset eventually appears because `flutter.yml` and `release.yml` run in parallel on the same tag; if the polling times out, the server image ships without the bundled update channel (graceful degradation, not a build failure).
-- **Cache server reachability.** `test-web.yml` does NOT use `cache: 'npm'` on `actions/setup-node` — the Forgejo Actions cache server isn't reachable from this runner's container network and `setup-node` was burning ~4m41s on ETIMEDOUT before failing open. With the migration to `ci-go:1.26`, `setup-node` is removed entirely (Node is in the image). The cache concern reappears if a future change re-introduces a network-dependent action.
+- **In-app update channel polling.** `release.yml` polls Gitea's release-asset API for up to 15 min on tag pushes to fetch the APK that `flutter.yml` is concurrently attaching to the same release. The asset eventually appears because `flutter.yml` and `release.yml` run in parallel on the same tag; if the polling times out, the server image ships without the bundled update channel (graceful degradation, not a build failure).
+- **Cache server reachability.** `test-web.yml` does NOT use `cache: 'npm'` on `actions/setup-node` — the Gitea Actions cache server isn't reachable from this runner's container network and `setup-node` was burning ~4m41s on ETIMEDOUT before failing open. With the migration to `ci-go:1.26`, `setup-node` is removed entirely (Node is in the image). The cache concern reappears if a future change re-introduces a network-dependent action.
 - **Friction asks.** None pending. The two images cover everything Minstrel needs.