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).

DOCKER_HUB.md

@@ -490,7 +490,7 @@ To override with your host's own files, uncomment the matching bind-mount lines
 - **opencode** — AI coding assistant
 - **Node.js 22** — for npx-based MCP servers
 - **AWS CLI v2** — SSO and Bedrock authentication
-- **Dev tools** — git, git-lfs, git-crypt, age, ssh, ripgrep, fd, fzf, bat, eza, zoxide, uv, rustup, mempalace, jq, make, gcc, g++, curl, wget, neovim 0.12, tmux, htop, tree, rsync
+- **Dev tools** — git, git-lfs, git-crypt, age, ssh, ripgrep, fd, fzf, bat, eza, zoxide, uv, rustup, mempalace, gitea-mcp, jq, make, gcc, g++, curl, wget, neovim 0.12, tmux, htop, tree, rsync
 - **Non-root user** — runs as `developer` with UID auto-matched to workspace owner (sudo available)
 
 ### OMOS image (`latest-omos`)