CREATE TABLE IF NOT EXISTS inbox (
    id INTEGER PRIMARY KEY AUTOINCREMENT,
    user_id TEXT NOT NULL REFERENCES users(id),
    message_id TEXT NOT NULL REFERENCES messages(id),
    channel_id TEXT NOT NULL,
    trigger TEXT NOT NULL CHECK (trigger IN ('mention', 'watch', 'broadcast')),
    acked_at TEXT,
    created_at TEXT NOT NULL DEFAULT (strftime('%Y-%m-%dT%H:%M:%SZ', 'now'))
);

CREATE INDEX IF NOT EXISTS idx_inbox_user_unacked ON inbox(user_id, acked_at);