feat: add Gitea as Archipelago app with container registry

Gitea app manifest, marketplace entry, nginx proxy, app session config,
image version, package install config. Container registry enabled on
Gitea for fallback image hosting. Trusted registries updated.

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

apps/gitea/manifest.yml

@@ -0,0 +1,42 @@
+id: gitea
+name: Gitea
+version: "1.23"
+description: Self-hosted Git service with built-in container registry, CI/CD, and package hosting.
+category: development
+icon: git-branch
+port: 3000
+ssh_port: 2222
+image: docker.io/gitea/gitea:1.23
+tier: optional
+
+requires:
+  memory_mb: 256
+  disk_mb: 500
+
+volumes:
+  - host: /var/lib/archipelago/gitea/data
+    container: /data
+  - host: /var/lib/archipelago/gitea/config
+    container: /etc/gitea
+
+environment:
+  GITEA__database__DB_TYPE: sqlite3
+  GITEA__server__SSH_PORT: "2222"
+  GITEA__server__SSH_LISTEN_PORT: "22"
+  GITEA__server__LFS_START_SERVER: "true"
+  GITEA__packages__ENABLED: "true"
+  GITEA__repository__ENABLE_PUSH_CREATE_USER: "true"
+  GITEA__repository__ENABLE_PUSH_CREATE_ORG: "true"
+
+health_check:
+  endpoint: /
+  interval: 120
+  timeout: 5
+  retries: 3
+
+features:
+  - Git repositories with web UI
+  - Built-in container/package registry
+  - Issue tracking and pull requests
+  - CI/CD via Gitea Actions
+  - Lightweight (SQLite, no external DB needed)