Add Deactivate Jail button for inactive jails with local override

- Add has_local_override field to InactiveJail model
- Update _build_inactive_jail and list_inactive_jails to compute the field
- Add delete_jail_local_override() service function
- Add DELETE /api/config/jails/{name}/local router endpoint
- Surface has_local_override in frontend InactiveJail type
- Show Deactivate Jail button in JailsTab when has_local_override is true
- Add tests: TestBuildInactiveJail, TestListInactiveJails, TestDeleteJailLocalOverride

backend/app/models/config.py

@@ -807,6 +807,14 @@ class InactiveJail(BaseModel):
             "inactive jails that appear in this list."
         ),
     )
+    has_local_override: bool = Field(
+        default=False,
+        description=(
+            "``True`` when a ``jail.d/{name}.local`` file exists for this jail. "
+            "Only meaningful for inactive jails; indicates that a cleanup action "
+            "is available."
+        ),
+    )
 
 
 class InactiveJailListResponse(BaseModel):