feat(whatsapp): QWEN primary AI backend, Hermes fallback, conversation history, vehicle persistence, demo prompts

- Add QWEN (qwen3.6) as primary AI backend with short system prompt
- Hermes remains as fallback with 45s timeout
- Increase QWEN timeout to 35s, max_tokens to 4000
- Add conversation history loading from whatsapp_messages (last 4 msgs)
- Persist detected vehicle in whatsapp_sessions table
- Add 'limpiar chat' / 'nuevo chat' / 'reset' commands to clear history
- Fix CSS conflict: rename whatsapp chat-panel classes to wa-chat-panel
- Fix JS ID conflicts with chat.js widget (waChatPanel, waChatMessages, etc.)
- Improve no-stock response: conversational with alternatives
- Split search_query by | for multi-part lookups
- Add DEMO_PROMPTS.md and DEMO_PROMPTS_V2.md

pos/services/quote_reservation.py

@@ -0,0 +1,123 @@
+"""Quotation stock reservation engine.
+
+Uses inventory_operations with operation types:
+  QUOTE_RESERVE  — negative quantity, reserves stock when quote is created
+  QUOTE_RELEASE  — positive quantity, restores stock when quote is cancelled/expired
+  QUOTE_CONVERT  — neutral (just a marker), actual sale uses SALE operation
+
+The trigger update_stock_summary() recalculates inventory_stock_summary
+by summing ALL operations, so reservations automatically affect visible stock.
+"""
+from services.inventory_engine import record_operation
+
+
+def reserve_for_quotation(conn, quotation_id, items, employee_id=None):
+    """Reserve stock for each item in a new quotation.
+
+    Args:
+        conn: tenant DB connection (not committed by this function).
+        quotation_id: the quotations.id.
+        items: list of dicts with inventory_id, quantity, branch_id (optional).
+        employee_id: optional, passed explicitly when g.employee_id is unavailable.
+    Returns:
+        list of operation IDs.
+    """
+    op_ids = []
+    for item in items:
+        inv_id = item.get('inventory_id')
+        qty = item.get('quantity', 0)
+        branch_id = item.get('branch_id')
+        if not inv_id or qty <= 0:
+            continue
+        op_id = record_operation(
+            conn, inv_id, branch_id, 'QUOTE_RESERVE',
+            quantity=-qty,
+            reference_id=quotation_id,
+            reference_type='quotation',
+            notes=f'Reserva cotizacion #{quotation_id}'
+        )
+        op_ids.append(op_id)
+    return op_ids
+
+
+def release_quotation_reservation(conn, quotation_id, items, employee_id=None):
+    """Release previously reserved stock (cancel, expire, or convert).
+
+    Args:
+        conn: tenant DB connection.
+        quotation_id: the quotations.id.
+        items: list of dicts with inventory_id, quantity, branch_id.
+        employee_id: optional.
+    Returns:
+        list of operation IDs.
+    """
+    op_ids = []
+    for item in items:
+        inv_id = item.get('inventory_id')
+        qty = item.get('quantity', 0)
+        branch_id = item.get('branch_id')
+        if not inv_id or qty <= 0:
+            continue
+        op_id = record_operation(
+            conn, inv_id, branch_id, 'QUOTE_RELEASE',
+            quantity=qty,
+            reference_id=quotation_id,
+            reference_type='quotation',
+            notes=f'Liberacion cotizacion #{quotation_id}'
+        )
+        op_ids.append(op_id)
+    return op_ids
+
+
+def convert_quotation_reservation(conn, quotation_id, items, sale_id=None, employee_id=None):
+    """Convert reservation to actual sale.
+
+    Flow:
+      1. Release the reservation (QUOTE_RELEASE +qty)
+      2. Record the actual sale (SALE -qty)
+
+    Args:
+        conn: tenant DB connection.
+        quotation_id: the quotations.id.
+        items: list of dicts with inventory_id, quantity, branch_id.
+        sale_id: the resulting sales.id (for reference).
+        employee_id: optional.
+    Returns:
+        list of operation IDs.
+    """
+    op_ids = release_quotation_reservation(conn, quotation_id, items, employee_id)
+    for item in items:
+        inv_id = item.get('inventory_id')
+        qty = item.get('quantity', 0)
+        branch_id = item.get('branch_id')
+        if not inv_id or qty <= 0:
+            continue
+        op_id = record_operation(
+            conn, inv_id, branch_id, 'SALE',
+            quantity=-qty,
+            reference_id=sale_id or quotation_id,
+            reference_type='sale' if sale_id else 'quotation',
+            notes=f'Venta convertida de cotizacion #{quotation_id}'
+        )
+        op_ids.append(op_id)
+    return op_ids
+
+
+def get_quotation_items_for_reservation(conn, quotation_id):
+    """Fetch items from a quotation joined with inventory to get branch_id.
+
+    Returns list of dicts: {inventory_id, quantity, branch_id}
+    """
+    cur = conn.cursor()
+    cur.execute("""
+        SELECT qi.inventory_id, qi.quantity, i.branch_id
+        FROM quotation_items qi
+        JOIN inventory i ON i.id = qi.inventory_id
+        WHERE qi.quotation_id = %s
+    """, (quotation_id,))
+    rows = cur.fetchall()
+    cur.close()
+    return [
+        {'inventory_id': r[0], 'quantity': r[1], 'branch_id': r[2]}
+        for r in rows
+    ]