feat(pos): WhatsApp Business API integration — send/receive messages, quotations

Add full WhatsApp Cloud API integration for Nexus POS:
- Service layer (whatsapp_service.py): send text, templates, quotations,
  order confirmations, stock alerts; process incoming webhooks with AI auto-reply
- Blueprint (whatsapp_bp.py): public webhook endpoints for Meta verification +
  incoming messages; authenticated endpoints for send, send-quote, conversations
- Conversation UI (whatsapp.html + whatsapp.js): split-panel messenger with
  conversation list, chat bubbles, send input, quote sending; both themes
- Migration v1.4: whatsapp_messages table with phone/direction/status indexes
- Config: WHATSAPP_TOKEN, WHATSAPP_PHONE_ID, WHATSAPP_VERIFY_TOKEN env vars
- Sidebar: WhatsApp nav item under Gestion with message-bubble icon
- Ready for Meta Business credentials (infrastructure complete, no API keys needed)

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

pos/migrations/runner.py

@@ -14,6 +14,8 @@ MIGRATIONS_DIR = os.path.dirname(os.path.abspath(__file__))
 MIGRATIONS = {
     'v1.0': 'v1.0_initial.sql',
     'v1.1': 'v1.1_pos_tables.sql',
+    'v1.3': 'v1.3_fleet.sql',
+    'v1.4': 'v1.4_whatsapp.sql',
 }
 
 

pos/migrations/v1.4_whatsapp.sql

@@ -0,0 +1,18 @@
+-- v1.4_whatsapp.sql — WhatsApp message history
+-- Applied per-tenant database
+
+CREATE TABLE IF NOT EXISTS whatsapp_messages (
+    id SERIAL PRIMARY KEY,
+    phone VARCHAR(20) NOT NULL,
+    direction VARCHAR(10) NOT NULL,  -- 'incoming' or 'outgoing'
+    message_text TEXT,
+    message_type VARCHAR(20) DEFAULT 'text',
+    wa_message_id VARCHAR(100),
+    status VARCHAR(20) DEFAULT 'sent',
+    related_type VARCHAR(50),  -- 'quotation', 'sale', 'alert'
+    related_id INTEGER,
+    created_at TIMESTAMPTZ DEFAULT NOW()
+);
+
+CREATE INDEX IF NOT EXISTS idx_wa_messages_phone ON whatsapp_messages(phone);
+CREATE INDEX IF NOT EXISTS idx_wa_messages_created ON whatsapp_messages(created_at DESC);