fix(gitea): wire real gitea-mcp server config into plugins/gitea/.mcp.json

Replace the empty mcpServers shell left by the deep-modules split
(ADR-0011) with a real, portable gitea-mcp server entry:

- Pin the server to v1.7.0 rather than @latest, since this is a
  checked-in, distributed artifact and an unpinned version would
  silently change on every future install.
- Use the bare "go" command, relying on PATH, instead of a
  machine-specific absolute path — mirroring the existing "npx"
  precedent for the obsidian entry in plugins/bin/.mcp.json.
- Require GITEA_ACCESS_TOKEN and GITEA_HOST via ${VAR} expansion with
  no inline defaults, so no secret or host value is hardcoded anywhere
  in the repo.

Refs #66.

Co-Authored-By: Claude Sonnet 5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01PDj6F7SPXzh3FtPN78dZ88

plugins/gitea/.mcp.json

@@ -1,3 +1,18 @@
 {
-  "mcpServers": {}
+  "mcpServers": {
+    "gitea": {
+      "args": [
+        "run",
+        "gitea.com/gitea/gitea-mcp@v1.7.0",
+        "-t",
+        "stdio"
+      ],
+      "command": "go",
+      "env": {
+        "GITEA_ACCESS_TOKEN": "${GITEA_ACCESS_TOKEN}",
+        "GITEA_HOST": "${GITEA_HOST}"
+      },
+      "type": "stdio"
+    }
+  }
 }