Add occupancy pick-up history + bookability history popup

Schema: migrate newbook_occupancy_report_data from single-row upsert to
snapshot model (drop unique constraint, add valid_from / last_verified_at)
matching the pattern used by newbook_current_rates.

Backend: sync_occupancy now inserts a new row only when occupied/available/
maintenance figures change, otherwise bumps last_verified_at. New endpoint
GET /bookability/occupancy-history/{category_id}/{date} returns the timeline.
Rate matrix query updated to DISTINCT ON for the multi-row table.

Frontend: clicking any cell in the Bookability matrix opens a modal with
two stacked Plotly charts — rate history per tariff (step lines, green/red
markers for available/unavailable) and occupancy pick-up over time.

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

backend/api/bookability.py

@@ -259,9 +259,10 @@ async def get_rate_matrix(
     rates_result = await db.execute(text(rates_query), rates_params)
     rates_rows = rates_result.fetchall()
 
-    # Fetch occupancy data from newbook_occupancy_report_data
+    # Fetch occupancy data — latest snapshot per category/date
     occupancy_query = """
-        SELECT category_id, date, occupied, available, maintenance
+        SELECT DISTINCT ON (category_id, date)
+            category_id, date, occupied, available, maintenance
         FROM newbook_occupancy_report_data
         WHERE date >= :from_date AND date <= :to_date
     """
@@ -271,6 +272,8 @@ async def get_rate_matrix(
         occupancy_query += " AND category_id = :category_id"
         occupancy_params["category_id"] = category_id
 
+    occupancy_query += " ORDER BY category_id, date, valid_from DESC"
+
     occupancy_result = await db.execute(text(occupancy_query), occupancy_params)
     occupancy_rows = occupancy_result.fetchall()
 
@@ -728,6 +731,56 @@ def _refresh_date_sync(rate_date: date):
         db.close()
 
 
+# ============================================
+# OCCUPANCY HISTORY ENDPOINT
+# ============================================
+
+@router.get("/occupancy-history/{category_id}/{rate_date}")
+async def get_occupancy_history(
+    category_id: str,
+    rate_date: str,
+    db: AsyncSession = Depends(get_db),
+    current_user: dict = Depends(get_current_user)
+):
+    """
+    Get occupancy snapshot history for a specific category and stay date.
+
+    Returns all snapshots where occupied/available/maintenance changed,
+    ordered oldest-first so the frontend can build a pick-up timeline.
+    """
+    try:
+        target_date = date.fromisoformat(rate_date)
+    except ValueError:
+        raise HTTPException(status_code=400, detail="Invalid date format. Use YYYY-MM-DD")
+
+    result = await db.execute(
+        text("""
+            SELECT valid_from, last_verified_at, occupied, available, maintenance, occupancy_pct
+            FROM newbook_occupancy_report_data
+            WHERE date = :date AND category_id = :category_id
+            ORDER BY valid_from ASC
+        """),
+        {"date": target_date, "category_id": category_id}
+    )
+
+    rows = result.fetchall()
+    return {
+        "category_id": category_id,
+        "rate_date": rate_date,
+        "snapshots": [
+            {
+                "valid_from": row.valid_from.isoformat() if row.valid_from else None,
+                "last_verified_at": row.last_verified_at.isoformat() if row.last_verified_at else None,
+                "occupied": row.occupied,
+                "available": row.available,
+                "maintenance": row.maintenance,
+                "occupancy_pct": float(row.occupancy_pct) if row.occupancy_pct is not None else None,
+            }
+            for row in rows
+        ],
+    }
+
+
 @router.post("/refresh-date/{rate_date}")
 async def refresh_single_date(
     rate_date: str,