task(E6-backend): guests CRUD - schema, adapter, routes

backend/src/database/schema.sql

@@ -178,3 +178,17 @@ CREATE TABLE IF NOT EXISTS global_blocks (
 
 CREATE INDEX IF NOT EXISTS idx_global_blocks_folder ON global_blocks(folder_id);
 CREATE INDEX IF NOT EXISTS idx_global_block_folders_parent ON global_block_folders(parent_id);
+
+-- ─── Guests (Task E6) ────────────────────────────────
+CREATE TABLE IF NOT EXISTS guests (
+  id TEXT PRIMARY KEY,
+  drawing_id TEXT NOT NULL,
+  name TEXT NOT NULL,
+  email TEXT,
+  category TEXT DEFAULT 'standard',
+  seat_element_id TEXT,
+  notes TEXT,
+  created_at TEXT NOT NULL DEFAULT (datetime('now')),
+  FOREIGN KEY (drawing_id) REFERENCES drawings(id) ON DELETE CASCADE
+);
+CREATE INDEX IF NOT EXISTS idx_guests_drawing ON guests(drawing_id);