Should you build your own Buffer?

Build me a personal social post scheduler to replace Buffer. Requirements:

- Node + Express + better-sqlite3; a localhost page with a compose box,
  image attach, and the queue ordered by send time.
- Two targets only: Mastodon (access token) and Bluesky (app password via
  @atproto/api), creds in .env. One small adapter file per network so a
  third is addable later, but scaffold nothing I don't use.
- Buffer-style slots: I define posting times (say weekdays 09:00 and 17:00
  in my timezone) and new posts fill the next free slot; a post can also be
  pinned to an exact datetime.
- A node-cron tick every minute publishes due posts, marks each row sent or
  failed, retries failures 3 times with backoff, and marks before sending so
  nothing ever double-posts.
- Per-network character counter in the composer; attached images stored in
  media/ next to the database.
- A history page of the last 100 sent posts linking to the live posts.
- Runs on my always-on box; localhost only, no accounts, no telemetry.
- Out of scope: X, Instagram, and LinkedIn (paid, approval-gated, or hostile
  APIs, say so in the README), analytics, and rich post previews.
- README: getting a Mastodon access token and a Bluesky app password.