fix(plan): make Plán prací usable on mobile + dev port → 3050

Mobile work-plan (Plán prací) responsive fixes — desktop unchanged:
- Toolbar stacks into clean full-width rows on ≤640px (nav group,
  centered range label, full-width segmented view toggle, full-width
  category button); drops the fixed 230px label min-width and the
  margin-left:auto that made the toolbar ragged on phones.
- Grid scroll container: 100dvh-based max-height, momentum scroll, and
  overscroll containment so a fling does not bounce the whole page.
- ≤480px tightens columns (date col 72px via the colgroup <col>, person
  cols 132px) so ~2 people are comfortably visible at 360–390px.
- Touch (@media hover:none): faint persistent + on empty editable
  cells, since the hover-reveal add hint never fires on a phone.

Dev: `npm run dev` (backend) now listens on 3050 instead of 3000 to
avoid colliding with other local apps; CLAUDE.md dev-port note updated.

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

CLAUDE.md

@@ -104,7 +104,7 @@ TOTP_ENCRYPTION_KEY=<64-char hex string>
 Optional (with defaults):
 
 ```
-PORT=3001                          # Production port (dev default: 3000)
+PORT=3001                          # Production port (dev default: 3050, hardcoded in server.ts)
 HOST=127.0.0.1
 APP_ENV=local|production           # Default: local. Controls CSP, CORS, HSTS
 ACCESS_TOKEN_EXPIRY=900            # 15 minutes