feat(wohnungen): "Rausgefilterte Wohnungen" section with reason chips

Below "Abgelehnte Wohnungen", surface flats that survived the time
filter and aren't rejected but failed at least one of the user's
filters. Same collapsed-card style. Action buttons are replaced by
chips naming each failed dimension — "Zimmer", "Preis", "Größe",
"WBS", "Bezirk" — so it's obvious which constraint to relax.

Refactored matching: flat_matches_filter now delegates to a new
flat_filter_failures(flat, f) that returns the failed-dimension
labels (empty list = full match). rooms_min and rooms_max collapse
to a single "Zimmer" chip; reasons emit in stable _REASON_ORDER for
consistent rendering. The section is suppressed entirely when the
user has no filters set, since "everything matches" makes the chips
meaningless.

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

web/matching.py

@@ -10,10 +10,23 @@ from typing import Iterable
 logger = logging.getLogger("web.matching")
 
 
-def flat_matches_filter(flat: dict, f: dict | None) -> bool:
-    """f is a user_filters row converted to dict (or None = no filter set)."""
+# German labels per filter dimension. The order also defines the order chips
+# appear in the "Rausgefilterte Wohnungen" section.
+_REASON_ORDER = ("Zimmer", "Preis", "Größe", "WBS", "Bezirk")
+
+
+def flat_filter_failures(flat: dict, f: dict | None) -> list[str]:
+    """Return the German labels of filter dimensions the flat fails. Empty list = full match.
+
+    Each label appears at most once (rooms_min and rooms_max both map to "Zimmer"),
+    in stable _REASON_ORDER so chips render consistently. Berlin-Bezirk filter:
+    empty string = no filter = all Bezirke match. When active, flats with an
+    unknown/unmapped PLZ count as a Bezirk failure — if the user bothered to
+    narrow by district, we shouldn't sneak in flats we couldn't place.
+    """
     if not f:
-        return True
+        return []
+    failures: set[str] = set()
 
     rooms = flat.get("rooms") or 0.0
     rent = flat.get("total_rent") or 0.0
@@ -21,34 +34,35 @@ def flat_matches_filter(flat: dict, f: dict | None) -> bool:
     wbs_str = str(flat.get("wbs", "")).strip().lower()
 
     if f.get("rooms_min") is not None and rooms < float(f["rooms_min"]):
-        return False
+        failures.add("Zimmer")
     if f.get("rooms_max") is not None and rooms > float(f["rooms_max"]):
-        return False
+        failures.add("Zimmer")
     if f.get("max_rent") is not None and rent > float(f["max_rent"]):
-        return False
+        failures.add("Preis")
     if f.get("min_size") is not None and size < float(f["min_size"]):
-        return False
+        failures.add("Größe")
 
     wbs_req = (f.get("wbs_required") or "").strip().lower()
     if wbs_req == "yes":
         if not wbs_str or wbs_str in ("kein", "nein", "no", "ohne", "-"):
-            return False
+            failures.add("WBS")
     elif wbs_req == "no":
         if wbs_str and wbs_str not in ("kein", "nein", "no", "ohne", "-"):
-            return False
+            failures.add("WBS")
 
-    # Berlin-Bezirk filter. Empty string = no filter = all Bezirke match.
-    # When active, flats with an unknown/unmapped PLZ are excluded — if the
-    # user bothered to narrow by district, we shouldn't sneak in flats we
-    # couldn't place.
     districts_csv = (f.get("districts") or "").strip()
     if districts_csv:
         selected = {d.strip() for d in districts_csv.split(",") if d.strip()}
         flat_district = (flat.get("district") or "").strip()
         if not flat_district or flat_district not in selected:
-            return False
+            failures.add("Bezirk")
 
-    return True
+    return [r for r in _REASON_ORDER if r in failures]
+
+
+def flat_matches_filter(flat: dict, f: dict | None) -> bool:
+    """f is a user_filters row converted to dict (or None = no filter set)."""
+    return not flat_filter_failures(flat, f)
 
 
 def row_to_dict(row) -> dict: