feat(apply): treat "Inserat offline" as its own outcome

Offline listings are a different class of result from real failures:
they mean "this ad is gone", not "the apply pipeline is broken".

- DB migration 0010 adds flats.offline_at; recent_flats() filters those
  out globally so they drop off every user's Wohnungen list
- _is_offline_result() matches the four known offline/deactivated
  phrases (DE + EN translations)
- On an offline result: mark the flat, reset the failure counter
  instead of incrementing, and skip the apply_fail notification
- Bewerbungen history renders a yellow "offline" chip in place of the
  red "fehlgeschlagen" one

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

web/common.py

@@ -202,6 +202,23 @@ def _has_running_application(user_id: int) -> bool:
     return db.has_running_application(user_id)
 
 
+# Apply returns success=False with one of these phrases when the listing has
+# been taken down or deactivated. We treat that as "the flat is gone" rather
+# than "the apply pipeline is broken" — no circuit-breaker hit, no fail
+# notification, and the flat is hidden from every user's list.
+_OFFLINE_MESSAGE_MARKERS = (
+    "inserat offline", "inserat deaktiviert",  # de
+    "ad offline", "ad deactivated",            # en
+)
+
+
+def _is_offline_result(message: str) -> bool:
+    if not message:
+        return False
+    m = message.lower()
+    return any(marker in m for marker in _OFFLINE_MESSAGE_MARKERS)
+
+
 def _finish_apply_background(app_id: int, user_id: int, flat_id: str, url: str,
                              profile: dict, submit_forms: bool) -> None:
     """Called on a worker thread AFTER the application row already exists.
@@ -218,8 +235,14 @@ def _finish_apply_background(app_id: int, user_id: int, flat_id: str, url: str,
     db.finish_application(app_id, success=success, message=message,
                           provider=provider, forensics=forensics)
 
+    offline = not success and _is_offline_result(message)
+    if offline:
+        db.mark_flat_offline(flat_id)
+
     prefs = db.get_preferences(user_id)
-    if success:
+    if success or offline:
+        # Offline isn't a pipeline failure — reset the counter so a streak of
+        # stale listings doesn't trip the circuit breaker.
         db.update_preferences(user_id, {"apply_recent_failures": 0})
     else:
         failures = int(prefs["apply_recent_failures"] or 0) + 1
@@ -241,10 +264,12 @@ def _finish_apply_background(app_id: int, user_id: int, flat_id: str, url: str,
                  "total_rent": flat["total_rent"] if flat else None}
     if success:
         notifications.on_apply_ok(user_id, flat_dict, message)
-    else:
+    elif not offline:
         notifications.on_apply_fail(user_id, flat_dict, message)
 
-    db.log_audit("system", "apply_finished", f"app={app_id} success={success}", user_id=user_id)
+    outcome = "success" if success else ("offline" if offline else "failure")
+    db.log_audit("system", "apply_finished",
+                 f"app={app_id} outcome={outcome}", user_id=user_id)
 
 
 def _kick_apply(user_id: int, flat_id: str, url: str, triggered_by: str) -> None: