Add SQL init fallback for todos table creation

backend/init-todos.sql

@@ -0,0 +1,21 @@
+-- Create todo_priority enum if not exists
+DO $$ BEGIN
+  CREATE TYPE todo_priority AS ENUM ('high', 'medium', 'low', 'none');
+EXCEPTION WHEN duplicate_object THEN null;
+END $$;
+
+-- Create todos table if not exists
+CREATE TABLE IF NOT EXISTS todos (
+  id UUID PRIMARY KEY DEFAULT gen_random_uuid(),
+  user_id TEXT NOT NULL,
+  title TEXT NOT NULL,
+  description TEXT,
+  is_completed BOOLEAN NOT NULL DEFAULT false,
+  priority todo_priority NOT NULL DEFAULT 'none',
+  category TEXT,
+  due_date TIMESTAMPTZ,
+  completed_at TIMESTAMPTZ,
+  sort_order INTEGER NOT NULL DEFAULT 0,
+  created_at TIMESTAMPTZ NOT NULL DEFAULT now(),
+  updated_at TIMESTAMPTZ NOT NULL DEFAULT now()
+);