wohnungen: preserve map across HTMX polls, add rejected section, drop €/m²

- #flats-map uses hx-preserve; marker data moved to <script type="application/json">
  sibling that diffs+updates instead of rebuilding Leaflet every poll (fixes
  whitescreen + tiles rendering outside the card)
- upsert_flat backfills lat/lng on existing rows missing coords (older flats
  scraped before the lat/lng migration now appear on the map once alert re-submits)
- collapsible "Abgelehnte Wohnungen" section at the bottom with Wiederherstellen
- remove €/m² column from the list

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

web/app.py

@@ -404,6 +404,8 @@ def _wohnungen_context(user) -> dict:
         last = db.last_application_for_flat(uid, f["id"])
         flats_view.append({"row": f, "last": last})
 
+    rejected_view = db.rejected_flats(uid)
+
     allowed, reason = _manual_apply_allowed()
     alert_label, alert_chip = _alert_status(notif_row)
     has_running = _has_running_application(uid)
@@ -422,6 +424,7 @@ def _wohnungen_context(user) -> dict:
         })
     return {
         "flats": flats_view,
+        "rejected_flats": rejected_view,
         "map_points": map_points,
         "has_filters": _has_filters(filters_row),
         "alert_label": alert_label,
@@ -548,6 +551,20 @@ async def action_reject(
     return _wohnungen_partial_or_redirect(request, user)
 
 
+@app.post("/actions/unreject")
+async def action_unreject(
+    request: Request,
+    flat_id: str = Form(...),
+    csrf: str = Form(...),
+    user=Depends(require_user),
+):
+    require_csrf(user["id"], csrf)
+    db.unreject_flat(user["id"], flat_id)
+    db.log_audit(user["username"], "flat.unrejected", f"flat_id={flat_id}",
+                 user_id=user["id"], ip=client_ip(request))
+    return _wohnungen_partial_or_redirect(request, user)
+
+
 # ---------------------------------------------------------------------------
 # Tab: Bewerbungen
 # ---------------------------------------------------------------------------