Restore guestline-monitor features: room stock/occupancy, rate history, room stats

- dates endpoint now returns total_avail, benchmark rate (tier-resolved),
  min-stay nights, max_rooms (summed per-room stock) and friendly labels
- rooms endpoint groups by room with stock, occupancy, best/bench rate and
  nested rate plans; injects known-but-absent rooms; honours room_order
- new /history/{stay_date} endpoint: per room/rate series, benchmark mode,
  or overall availability + cheapest rate per scrape run
- new /stats endpoint: per-room stock + windowed avg rate / current occ /
  est. final occ (look-back window so past dates give completed bookings)
- DirectRates page: occupancy pills, avail x/stock, Room Stats tab,
  history chart modal (plotly), expandable rate plans with history links
- fix discovery trigger crashing (run_until_complete inside running loop)
- fix migration script reading wrong column name (engine_profile)

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>

backend/migrate_direct_data.py

@@ -10,6 +10,7 @@ import sys
 from datetime import datetime, timezone
 
 import psycopg2
+import psycopg2.extras
 
 ARCHIVE_DIR = os.environ.get(
     "GUESTLINE_ARCHIVE",
@@ -37,7 +38,7 @@ def migrate():
     src = sqlite3.connect(CONFIG_DB)
     src.row_factory = dict_row
     hotels = src.execute(
-        """SELECT id, name, profile, params, room_labels, rate_labels,
+        """SELECT id, name, engine_profile, params, room_labels, rate_labels,
                   room_order, benchmark_room, benchmark_rate,
                   tier_base_room, tier_offsets, scrape_enabled, last_scraped_at
            FROM hotels ORDER BY id"""
@@ -65,7 +66,7 @@ def migrate():
                    RETURNING id""",
                 (
                     h["name"],
-                    h["profile"],
+                    h["engine_profile"],
                     params,
                     h["room_labels"] or "{}",
                     h["rate_labels"] or "{}",
@@ -163,5 +164,4 @@ def migrate():
 
 
 if __name__ == "__main__":
-    import psycopg2.extras
     migrate()