Add official Gitea MCP server to base image

Install gitea-mcp v1.1.0 (Go binary from gitea.com/gitea/gitea-mcp)
using the same multi-arch pattern as gosu/fzf/bat. Provides 50+ MCP
tools for Gitea API — repos, issues, PRs, releases, branches, wiki,
and Actions.

Disabled by default in auto-generated opencode.json (requires
GITEA_ACCESS_TOKEN and GITEA_HOST to be useful). Users enable it by
setting those env vars in .env and flipping enabled to true in their
opencode.json.

Env vars forwarded into the container via docker-compose.yml and
docker-compose.shared.yml environment blocks. Same {env:VAR} pattern
as the GitHub MCP server.

Docs updated: README.md (new Gitea MCP section with setup steps),
DOCKER_HUB.md (tools list), CHANGELOG.md (v1.14.28b entry).

README.md

@@ -510,6 +510,38 @@ Both volumes are commented out by default in `docker-compose.yml` — uncomment
 
 **Air-gapped environments:** pre-populate the `devbox-chroma-cache` volume with the `all-MiniLM-L6-v2/` model contents. The palace volume needs no pre-population.
 
+## Gitea MCP server
+
+The image includes the [official Gitea MCP server](https://gitea.com/gitea/gitea-mcp) (`gitea-mcp`), providing 50+ MCP tools for interacting with self-hosted Gitea instances — repositories, issues, pull requests, releases, branches, wiki, and Actions.
+
+### Setup
+
+1. Create a Personal Access Token on your Gitea instance (Settings → Applications → Generate Token, scopes: `repo`, `read:user`).
+
+2. Add to your `.env`:
+   ```env
+   GITEA_HOST=https://your-gitea-instance.example.com
+   GITEA_ACCESS_TOKEN=your_token_here
+   ```
+
+3. Enable the gitea MCP server in your `opencode.json`:
+   ```json
+   {
+     "mcp": {
+       "gitea": {
+         "type": "local",
+         "command": ["gitea-mcp", "-t", "stdio", "--host", "{env:GITEA_HOST}"],
+         "environment": {
+           "GITEA_ACCESS_TOKEN": "{env:GITEA_ACCESS_TOKEN}"
+         },
+         "enabled": true
+       }
+     }
+   }
+   ```
+
+The server is installed but disabled by default — it requires authentication to be useful.
+
 ## Shell defaults
 
 The image ships a baked `.bash_aliases` and `.inputrc` with quality-of-life defaults. On first container start they are copied from `/etc/skel-devbox/` into `/home/developer/` **only if the target file does not already exist** — so host bind-mounts and any version you've customized inside the container are never overwritten on upgrade.