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/action_config.py

@@ -32,24 +32,6 @@ _NamePath = Annotated[
     Path(description='Jail name as configured in fail2ban.'),
 ]
 
-
-def _action_not_found(name: str) -> HTTPException:
-    return HTTPException(
-        status_code=status.HTTP_404_NOT_FOUND,
-        detail=f"Action not found: {name!r}",
-    )
-
-
-def _bad_request(message: str) -> HTTPException:
-    return HTTPException(status_code=status.HTTP_400_BAD_REQUEST, detail=message)
-
-
-def _not_found(name: str) -> HTTPException:
-    return HTTPException(
-        status_code=status.HTTP_404_NOT_FOUND,
-        detail=f"Jail not found: {name!r}",
-    )
-
 @router.get(
     "",
     response_model=ActionListResponse,
@@ -116,10 +98,7 @@ async def get_action(
     Raises:
         HTTPException: 404 if the action is not found in ``action.d/``.
     """
-    try:
-        return await action_config_service.get_action(config_dir, socket_path, name)
-    except ActionNotFoundError:
-        raise _action_not_found(name) from None
+    return await action_config_service.get_action(config_dir, socket_path, name)
 
 
 # ---------------------------------------------------------------------------
@@ -163,17 +142,7 @@ async def update_action(
         HTTPException: 404 if the action does not exist.
         HTTPException: 500 if writing the ``.local`` file fails.
     """
-    try:
-        return await action_config_service.update_action(config_dir, socket_path, name, body, do_reload=reload)
-    except ActionNameError as exc:
-        raise _bad_request(str(exc)) from exc
-    except ActionNotFoundError:
-        raise _action_not_found(name) from None
-    except ConfigWriteError as exc:
-        raise HTTPException(
-            status_code=status.HTTP_500_INTERNAL_SERVER_ERROR,
-            detail=f"Failed to write action override: {exc}",
-        ) from exc
+    return await action_config_service.update_action(config_dir, socket_path, name, body, do_reload=reload)
 
 
 
@@ -211,20 +180,7 @@ async def create_action(
         HTTPException: 409 if the action already exists.
         HTTPException: 500 if writing fails.
     """
-    try:
-        return await action_config_service.create_action(config_dir, socket_path, body, do_reload=reload)
-    except ActionNameError as exc:
-        raise _bad_request(str(exc)) from exc
-    except ActionAlreadyExistsError as exc:
-        raise HTTPException(
-            status_code=status.HTTP_409_CONFLICT,
-            detail=f"Action {exc.name!r} already exists.",
-        ) from exc
-    except ConfigWriteError as exc:
-        raise HTTPException(
-            status_code=status.HTTP_500_INTERNAL_SERVER_ERROR,
-            detail=f"Failed to write action: {exc}",
-        ) from exc
+    return await action_config_service.create_action(config_dir, socket_path, body, do_reload=reload)
 
 
 
@@ -256,22 +212,7 @@ async def delete_action(
         HTTPException: 409 if the action is a shipped default (conf-only).
         HTTPException: 500 if deletion fails.
     """
-    try:
-        await action_config_service.delete_action(config_dir, name)
-    except ActionNameError as exc:
-        raise _bad_request(str(exc)) from exc
-    except ActionNotFoundError:
-        raise _action_not_found(name) from None
-    except ActionReadonlyError as exc:
-        raise HTTPException(
-            status_code=status.HTTP_409_CONFLICT,
-            detail=str(exc),
-        ) from exc
-    except ConfigWriteError as exc:
-        raise HTTPException(
-            status_code=status.HTTP_500_INTERNAL_SERVER_ERROR,
-            detail=f"Failed to delete action: {exc}",
-        ) from exc
+    await action_config_service.delete_action(config_dir, name)