refactor: move repository and service imports to module level in dependencies.py

Move all repository imports (session_repo, blocklist_repo, import_log_repo,
settings_repo, history_archive_repo, geo_cache_repo, fail2ban_db_repo) and
service imports (auth_service, health_service, default_fail2ban_metadata_service)
to module level in app/dependencies.py.

This eliminates the pattern of local imports inside provider functions,
providing consistency and reducing import overhead. The from app.db import
open_db remains a local import since it's only used within get_db().

- Verified no circular dependencies exist
- All repository and service provider functions simplified to return modules
- Updated Architekture.md § 2.3 to document the module-level import pattern
- All tests pass (28 dependency + auth tests)

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

backend/app/dependencies.py

@@ -60,6 +60,20 @@ from app.utils.rate_limiter import RateLimiter
 from app.utils.runtime_state import ApplicationState, JailServiceState, RuntimeState
 from app.utils.session_cache import NoOpSessionCache, SessionCache
 
+# Module-level imports for repositories and services
+# These are safe at module level since no circular dependencies exist
+from app.repositories import (
+    blocklist_repo,
+    fail2ban_db_repo,
+    geo_cache_repo,
+    history_archive_repo,
+    import_log_repo,
+    session_repo,
+    settings_repo,
+)
+from app.services import auth_service, health_service
+from app.services.fail2ban_metadata_service import default_fail2ban_metadata_service
+
 log: structlog.stdlib.BoundLogger = structlog.get_logger()
 
 
@@ -255,8 +269,6 @@ async def get_session_repo() -> SessionRepository:
     Protocol interface — its top-level async functions must match the Protocol
     signatures exactly. This is documented in Backend-Development.md § 13.7.1.
     """
-    from app.repositories import session_repo  # noqa: PLC0415
-
     return session_repo
 
 
@@ -267,8 +279,6 @@ async def get_blocklist_repo() -> BlocklistRepository:
     Protocol interface — its top-level async functions must match the Protocol
     signatures exactly. This is documented in Backend-Development.md § 13.7.1.
     """
-    from app.repositories import blocklist_repo  # noqa: PLC0415
-
     return cast("BlocklistRepository", blocklist_repo)
 
 
@@ -279,8 +289,6 @@ async def get_import_log_repo() -> ImportLogRepository:
     Protocol interface — its top-level async functions must match the Protocol
     signatures exactly. This is documented in Backend-Development.md § 13.7.1.
     """
-    from app.repositories import import_log_repo  # noqa: PLC0415
-
     return cast("ImportLogRepository", import_log_repo)
 
 
@@ -291,8 +299,6 @@ async def get_settings_repo() -> SettingsRepository:
     Protocol interface — its top-level async functions must match the Protocol
     signatures exactly. This is documented in Backend-Development.md § 13.7.1.
     """
-    from app.repositories import settings_repo  # noqa: PLC0415
-
     return cast("SettingsRepository", settings_repo)
 
 
@@ -304,8 +310,6 @@ async def get_history_archive_repo() -> HistoryArchiveRepository:
     must match the Protocol signatures exactly. This is documented in
     Backend-Development.md § 13.7.1.
     """
-    from app.repositories import history_archive_repo  # noqa: PLC0415
-
     return cast("HistoryArchiveRepository", history_archive_repo)
 
 
@@ -316,8 +320,6 @@ async def get_geo_cache_repo() -> GeoCacheRepository:
     Protocol interface — its top-level async functions must match the Protocol
     signatures exactly. This is documented in Backend-Development.md § 13.7.1.
     """
-    from app.repositories import geo_cache_repo  # noqa: PLC0415
-
     return cast("GeoCacheRepository", geo_cache_repo)
 
 
@@ -329,8 +331,6 @@ async def get_fail2ban_db_repo() -> Fail2BanDbRepository:
     match the Protocol signatures exactly. This is documented in
     Backend-Development.md § 13.7.1.
     """
-    from app.repositories import fail2ban_db_repo  # noqa: PLC0415
-
     return cast("Fail2BanDbRepository", fail2ban_db_repo)
 
 
@@ -375,8 +375,6 @@ async def get_health_probe() -> Callable[[str], Awaitable[ServerStatus]]:
         A callable that probes the fail2ban socket and returns ServerStatus.
         This allows explicit dependency injection to avoid hidden service coupling.
     """
-    from app.services import health_service  # noqa: PLC0415
-
     return health_service.probe
 
 
@@ -387,8 +385,6 @@ async def get_fail2ban_metadata_service() -> object:
         The singleton Fail2BanMetadataService for resolving fail2ban metadata
         (such as the database path) and caching results.
     """
-    from app.services.fail2ban_metadata_service import default_fail2ban_metadata_service  # noqa: PLC0415
-
     return default_fail2ban_metadata_service
 
 
@@ -612,8 +608,6 @@ async def require_auth(
         if cached is not None:
             return cached
 
-    from app.services import auth_service  # noqa: PLC0415
-
     try:
         session = await auth_service.validate_session(
             db,