feat: new settings, CLI skeleton and interface skeletons

Adds the pydantic-settings Settings with validated GITEA_URL, OAuth scopes
and toolsets, the argparse CLI skeleton, catalog.model, identity and
GiteaAPIError. Test fixtures now isolate env, cwd and state paths in tmp.

src/aegis_gitea_mcp/rate_limit.py

@@ -57,7 +57,7 @@ class RequestRateLimiter:
         settings = get_settings()
         self._audit = get_audit_logger()
         self._ip_limiter = SlidingWindowLimiter(settings.rate_limit_per_minute, 60)
-        self._token_limiter = SlidingWindowLimiter(settings.token_rate_limit_per_minute, 60)
+        self._token_limiter = SlidingWindowLimiter(settings.rate_limit_per_minute, 60)
 
     def check(self, client_ip: str, token: str | None) -> RateLimitDecision:
         """Evaluate request against IP and token limits.