feat: Complete repository protocol coverage

- Add missing protocol methods to Fail2BanDbRepository:
  - get_ban_event_counts: Aggregate ban events per IP (used in ban_service)

- Add missing protocol methods to GeoCacheRepository:
  - delete_stale_entries: Remove old geo cache entries (used in geo_cache_cleanup)

- Add missing protocol methods to HistoryArchiveRepository:
  - purge_archived_history: Remove archived entries older than age threshold

- Add comprehensive protocol compliance tests:
  - Created test_protocol_compliance.py with 8 test classes
  - Validates all 7 repository modules fully implement their protocols
  - Prevents silent protocol drift when methods change signatures
  - Tests verify no unexpected public methods in repository modules

- Update documentation:
  - Add Repository Protocol Coverage Checklist to Backend-Development.md
  - Document procedure for adding new repositories with protocol definitions
  - List current protocol coverage (all 7 repositories, 40 total methods)

- All repositories now have 100% protocol coverage:
  - SessionRepository: 4 methods
  - SettingsRepository: 4 methods
  - BlocklistRepository: 6 methods
  - ImportLogRepository: 4 methods
  - GeoCacheRepository: 13 methods
  - HistoryArchiveRepository: 5 methods
  - Fail2BanDbRepository: 8 methods

This ensures:
- Enhanced mockability for testing
- Static contract verification
- Prevention of protocol drift
- Better IDE support and type checking

Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>

backend/app/repositories/protocols.py

@@ -13,7 +13,7 @@ import aiosqlite
 
 from app.models.auth import Session
 from app.models.ban import BanOrigin
-from app.repositories.fail2ban_db_repo import BanRecord, HistoryRecord, JailBanCount
+from app.repositories.fail2ban_db_repo import BanIpCount, BanRecord, HistoryRecord, JailBanCount
 from app.repositories.geo_cache_repo import GeoCacheRow
 from app.repositories.import_log_repo import ImportLogRow
 
@@ -203,6 +203,9 @@ class GeoCacheRepository(Protocol):
     ) -> tuple[int, int]:
         ...
 
+    async def delete_stale_entries(self, db: aiosqlite.Connection, cutoff_iso: str) -> int:
+        ...
+
 
 class HistoryArchiveRepository(Protocol):
     """Protocol for archived ban history persistence operations."""
@@ -246,6 +249,9 @@ class HistoryArchiveRepository(Protocol):
     ) -> list[dict[str, Any]]:
         ...
 
+    async def purge_archived_history(self, db: aiosqlite.Connection, age_seconds: int) -> int:
+        ...
+
 
 class Fail2BanDbRepository(Protocol):
     async def check_db_nonempty(self, db_path: str) -> bool:
@@ -273,6 +279,14 @@ class Fail2BanDbRepository(Protocol):
     ) -> list[int]:
         ...
 
+    async def get_ban_event_counts(
+        self,
+        db_path: str,
+        since: int,
+        origin: BanOrigin | None = None,
+    ) -> list[BanIpCount]:
+        ...
+
     async def get_bans_by_jail(
         self,
         db_path: str,