feat(inventory): dynamic tab badges with real tenant data

- Add /pos/api/inventory/stats endpoint returning counts per tab
- Replace hardcoded badge numbers (4,817, 14, 3, 23) with dynamic values
- Frontend auto-fetches stats on page load and updates badges

pos/blueprints/inventory_bp.py

@@ -809,6 +809,52 @@ def physical_count_approve():
     })
 
 
+# ─── Stats Summary ─────────────────────────────
+
+@inventory_bp.route('/stats', methods=['GET'])
+@require_auth('inventory.view')
+def api_inventory_stats():
+    """Get inventory summary counts for dashboard badges."""
+    conn = get_tenant_conn(g.tenant_id)
+    cur = conn.cursor()
+    branch_id = getattr(g, 'branch_id', None)
+
+    # Stock count
+    cur.execute("SELECT COUNT(*) FROM inventory WHERE is_active = true AND (branch_id = %s OR %s IS NULL)", (branch_id, branch_id))
+    stock = cur.fetchone()[0]
+
+    # Operations counts by type
+    cur.execute("""
+        SELECT operation_type, COUNT(*) 
+        FROM inventory_operations 
+        WHERE (branch_id = %s OR %s IS NULL)
+        GROUP BY operation_type
+    """, (branch_id, branch_id))
+    op_counts = {row[0]: row[1] for row in cur.fetchall()}
+
+    # Physical counts
+    cur.execute("SELECT COUNT(*) FROM physical_counts WHERE (branch_id = %s OR %s IS NULL)", (branch_id, branch_id))
+    physical = cur.fetchone()[0]
+
+    cur.close()
+    conn.close()
+
+    # Alerts (reuse existing function)
+    conn2 = get_tenant_conn(g.tenant_id)
+    alerts_list = get_alerts(conn2, branch_id)
+    conn2.close()
+
+    return jsonify({
+        'stock': stock,
+        'entradas': op_counts.get('PURCHASE', 0),
+        'salidas': op_counts.get('SALE', 0),
+        'traspasos': op_counts.get('TRANSFER', 0),
+        'ajustes': op_counts.get('ADJUST', 0),
+        'conteos': physical,
+        'alertas': len(alerts_list)
+    })
+
+
 # ─── Alerts and History ────────────────────────
 
 @inventory_bp.route('/alerts', methods=['GET'])