refactor: make gitea a self-contained Cline skill

Relocate the script into the skill (skills/gitea/scripts/gitea_mcp.py) and add a
PEP 723 dependency block, so `uv run scripts/gitea_mcp.py` provisions deps with no
install step and the skill folder is portable (drop into ~/.cline/skills/). Drop
the non-standard `metadata` frontmatter — Cline only recognizes name + description.

- .mcp.json points at the relocated script and runs with --no-project (PEP 723)
- SKILL.md uses relative scripts/ paths; metadata block removed
- find_config walks up the tree to locate config.json (skill root or plugin root)
- tests import gitea_mcp via pytest pythonpath; README/CLAUDE paths updated

Tests: 119 passed, 92% coverage. Standalone list-tools verified via uv --no-project.

tests/conftest.py

@@ -1,6 +1,6 @@
 import os
 from pathlib import Path
 
-# Must be set at module level, before any import of server.gitea_mcp,
+# Must be set at module level, before any import of gitea_mcp,
 # so find_config() picks up the test credentials instead of the real config.json.
 os.environ.setdefault("GITEA_CONFIG", str(Path(__file__).parent / "config.test.json"))