feat(security): resource-type-aware authorization with fail-closed defaults

Add aegis_gitea_mcp.authz: classify every dispatched call (typed tools and
gitea_request) by resource type (repository/org/user_self/user_owned/
misc_global/admin/unknown) and enforce a type-specific rule in service-PAT
mode, on top of policy + WRITE_MODE. Every decision fails closed:

- org: signed-in user must be a verified org member (Gitea-checked).
- user_owned: owner must be the caller or a member org of the caller.
- user_self: token-owner-scoped endpoints denied (token is the bot's).
- admin: default-deny; allowed only with RAW_API_ALLOW_SENSITIVE opt-in AND a
  verified site admin.
- misc_global: reads allowed, writes denied.
- unknown / unverifiable: denied and audited.

Wire it into the server's service-PAT dispatch: repository calls keep the
existing per-user collaborator check; non-repo calls (previously blanket-denied)
now go through the resource-type gate, opening the org/user/admin surface
safely. Verification results are cached briefly (fail-closed: positives only).

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

tests/conftest.py

@@ -7,6 +7,7 @@ import pytest
 
 from aegis_gitea_mcp.audit import reset_audit_logger
 from aegis_gitea_mcp.auth import reset_validator
+from aegis_gitea_mcp.authz import reset_authz_caches
 from aegis_gitea_mcp.config import reset_settings
 from aegis_gitea_mcp.oauth import reset_oauth_validator
 from aegis_gitea_mcp.oauth_flow import reset_oauth_client_registry
@@ -27,6 +28,7 @@ def reset_globals(tmp_path: Path, monkeypatch: pytest.MonkeyPatch) -> Generator[
     reset_oauth_validator()
     reset_oauth_client_registry()
     reset_repo_authz_cache()
+    reset_authz_caches()
     reset_policy_engine()
     reset_rate_limiter()
     reset_metrics_registry()
@@ -45,6 +47,7 @@ def reset_globals(tmp_path: Path, monkeypatch: pytest.MonkeyPatch) -> Generator[
     reset_oauth_validator()
     reset_oauth_client_registry()
     reset_repo_authz_cache()
+    reset_authz_caches()
     reset_policy_engine()
     reset_rate_limiter()
     reset_metrics_registry()