Add Timelog: show the timer in the tab title and simplify the code

This is the first commit of the project, at the state that runs on
timelog.minhtrannhat.com.

Changes in this state:
- Remove redundant UI text from the sidebar, timer and insights pages.
- Show the remaining time and tag in the browser tab title while a
  session runs.
- Put the shared record type and the due and end helpers in
  src/shared/record.ts.
- Remove the startup tag migration and the one-time Forest import
  script. The live data does not need them.
- Remove unused CSS, Playwright ignore rules and duplicate helpers.
- Do not track Forest CSV exports, because they contain private data.

Co-Authored-By: Claude Opus 5.5 <[email protected]>

scripts/vapid.ts

@@ -0,0 +1,5 @@
+import webpush from "web-push";
+
+const keys = webpush.generateVAPIDKeys();
+console.log(`VAPID_PUBLIC_KEY=${keys.publicKey}`);
+console.log(`VAPID_PRIVATE_KEY=${keys.privateKey}`);