Chores: weekly goals with custom reward tiers (everyone or chosen people)

- Admin-set reward tiers; points count Monday to Sunday and restart each week
- Per-person weekly totals, chores done, progress bar toward the next reward, week history
- Mark given / undo when a reward is handed over
- Rewards can be for everyone or only chosen people
- "This week" card on the family board
- Tests and README updated

Co-Authored-By: Claude Sonnet 5.5 <noreply@anthropic.com>

public/sw.js

@@ -1,5 +1,5 @@
 // App-shell cache only; Seafile/API traffic always goes to the network.
-const CACHE = 'hub-v75';
+const CACHE = 'hub-v77';
 const SHARE = 'hub-share'; // files shared into the app from other apps, held until the person picks a folder
 const SHELL = ['/icon.svg', '/manifest.webmanifest', '/icons/icon-192.png', '/icons/apple-touch-icon.png'];