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/geo.py

@@ -13,7 +13,7 @@ from typing import TYPE_CHECKING, Annotated
 if TYPE_CHECKING:
     from app.services.jail_service import IpLookupResult
 
-from fastapi import APIRouter, HTTPException, Path, status
+from fastapi import APIRouter, Path
 
 from app.dependencies import (
     AuthDep,
@@ -21,7 +21,6 @@ from app.dependencies import (
     Fail2BanSocketDep,
     HttpSessionDep,
 )
-from app.exceptions import Fail2BanConnectionError
 from app.models.geo import GeoCacheStatsResponse, GeoReResolveResponse, IpLookupResponse
 from app.services import geo_service, jail_service
 
@@ -58,22 +57,11 @@ async def lookup_ip(
         HTTPException: 400 when *ip* is not a valid IP address.
         HTTPException: 502 when fail2ban is unreachable.
     """
-    try:
-        result: IpLookupResult = await jail_service.lookup_ip(
-            socket_path,
-            ip,
-            http_session=http_session,
-        )
-    except ValueError as exc:
-        raise HTTPException(
-            status_code=status.HTTP_400_BAD_REQUEST,
-            detail=str(exc),
-        ) from exc
-    except Fail2BanConnectionError as exc:
-        raise HTTPException(
-            status_code=status.HTTP_502_BAD_GATEWAY,
-            detail=f"Cannot reach fail2ban: {exc}",
-        ) from exc
+    result: IpLookupResult = await jail_service.lookup_ip(
+        socket_path,
+        ip,
+        http_session=http_session,
+    )
 
     return IpLookupResponse(**result)