CREATE TABLE ai_usage (
    id INTEGER PRIMARY KEY,
    user_id INTEGER NOT NULL REFERENCES users(id) ON DELETE CASCADE,
    model TEXT NOT NULL,
    endpoint TEXT NOT NULL,
    prompt_tokens INTEGER NOT NULL,
    completion_tokens INTEGER NOT NULL,
    total_tokens INTEGER NOT NULL,
    cost REAL NOT NULL,
    created_at TEXT NOT NULL DEFAULT (strftime('%Y-%m-%dT%H:%M:%fZ', 'now'))
);

CREATE INDEX idx_ai_usage_user_id ON ai_usage(user_id);