refactor: Remove duplicate router-level exception helpers

All routers now let domain exceptions propagate to the global handlers in main.py
instead of catching and converting them to HTTPException. This eliminates:

- Duplicate exception-to-HTTP-status mappings across 8 routers
- Duplicate helper functions (_bad_gateway, _not_found, _conflict, etc.)
- Inconsistent error response formats

Changes:
- Removed all try/except blocks from routers that catch domain exceptions
- Removed duplicate helper functions from all routers
- Added missing exception handlers to main.py for:
  * ActionNameError
  * FilterNameError
  * JailNameError
  * JailNotFoundInConfigError
  * FilterInvalidRegexError
- Removed unused imports from affected routers

All domain exceptions now propagate to the single authoritative mapping in
main.py, ensuring consistent error codes, messages, and logging across the API.

Affected routers:
- action_config.py: Removed _action_not_found, _bad_request, _not_found helpers
- bans.py: Removed try/except in ban/unban endpoints
- config_misc.py: Removed try/except blocks
- file_config.py: Removed 6 try/except blocks and _service_unavailable helper
- filter_config.py: Removed try/except blocks
- geo.py: Removed try/except in lookup_ip endpoint
- jail_config.py: Removed try/except blocks
- jails.py: Removed try/except blocks
- server.py: Removed try/except blocks

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

backend/app/routers/server.py

@@ -15,31 +15,11 @@ from fastapi import APIRouter, HTTPException, Request, status
 from app.dependencies import AuthDep, Fail2BanSocketDep
 from app.models.server import ServerSettingsResponse, ServerSettingsUpdate
 from app.services import server_service
-from app.exceptions import ServerOperationError
-from app.exceptions import Fail2BanConnectionError
+from app.exceptions import ServerOperationError, Fail2BanConnectionError
 
 router: APIRouter = APIRouter(prefix="/api/server", tags=["Server"])
 
 
-# ---------------------------------------------------------------------------
-# Helpers
-# ---------------------------------------------------------------------------
-
-
-def _bad_gateway(exc: Exception) -> HTTPException:
-    return HTTPException(
-        status_code=status.HTTP_502_BAD_GATEWAY,
-        detail=f"Cannot reach fail2ban: {exc}",
-    )
-
-
-def _bad_request(message: str) -> HTTPException:
-    return HTTPException(
-        status_code=status.HTTP_400_BAD_REQUEST,
-        detail=message,
-    )
-
-
 # ---------------------------------------------------------------------------
 # Endpoints
 # ---------------------------------------------------------------------------
@@ -70,10 +50,7 @@ async def get_server_settings(
     Raises:
         HTTPException: 502 when fail2ban is unreachable.
     """
-    try:
-        return await server_service.get_settings(socket_path)
-    except Fail2BanConnectionError as exc:
-        raise _bad_gateway(exc) from exc
+    return await server_service.get_settings(socket_path)
 
 
 @router.put(
@@ -101,12 +78,7 @@ async def update_server_settings(
         HTTPException: 400 when a set command is rejected by fail2ban.
         HTTPException: 502 when fail2ban is unreachable.
     """
-    try:
-        await server_service.update_settings(socket_path, body)
-    except ServerOperationError as exc:
-        raise _bad_request(str(exc)) from exc
-    except Fail2BanConnectionError as exc:
-        raise _bad_gateway(exc) from exc
+    await server_service.update_settings(socket_path, body)
 
 
 @router.post(
@@ -135,10 +107,5 @@ async def flush_logs(
         HTTPException: 400 when the command is rejected.
         HTTPException: 502 when fail2ban is unreachable.
     """
-    try:
-        result = await server_service.flush_logs(socket_path)
-        return {"message": result}
-    except ServerOperationError as exc:
-        raise _bad_request(str(exc)) from exc
-    except Fail2BanConnectionError as exc:
-        raise _bad_gateway(exc) from exc
+    result = await server_service.flush_logs(socket_path)
+    return {"message": result}