Stage 8 polish: profile validation, finished-game UI, badge + Safari fixes

Owner-review follow-up on the Stage 8 branch:
- Friend code is copyable (📋 + toast). The lobby notification badge is fixed —
  it had inherited the hamburger-bar style — into a proper round count dot.
- Safari: min-width:0 on flex text inputs (friend code, profile, chat) so they
  shrink instead of pushing the adjacent button off-screen.
- Profile editing is validated on both the UI and the backend: display-name format
  (letters joined by single space/./_ separators, no leading/trailing/adjacent
  separators, <=32 runes), a UTC-offset timezone picker (account.ResolveZone parses
  ±HH:MM or a legacy IANA name), a 10-minute away grid capped at 12h (wrap-aware),
  and email format; Save is disabled and invalid fields red-bordered until valid.
  Language stays in Settings.
- In a game, an "add to friends" menu item flips to a disabled "request sent"; chat
  send/nudge became ⬆️/🛎️ icon buttons.
- A finished game drops its last-word highlight, hides Check word / Drop game,
  disables zoom, and draws an inert (greyed) footer instead of hiding it.

Tests: account validators (name/away/zone), UI profileValidation, e2e for the
finished-game footer/menu and the copy control. Docs (PLAN, ARCHITECTURE,
FUNCTIONAL +ru, UI_DESIGN) updated for the display-name rule, UTC-offset timezone
and the 12h away window.

docs/UI_DESIGN.md

@@ -95,13 +95,23 @@ IV 🏅; active games show Your move 🟢 / Opponent's move ⏳; invitations use
 - **Statistics** (`screens/Stats.svelte`, the lobby 📊 tab): a 2-column grid of stat
   cards (wins / losses / draws / games / win-rate / best game / best move) — pure
   numbers, no charts.
-- **Profile editing** (`screens/Profile.svelte`): an inline form (display name, timezone,
-  the away-window time pickers, block toggles) and an email-binding sub-flow (enter email
-  → enter the confirm code). Interface language stays in **Settings** (it writes through
-  to the account for durable users).
+- **Profile editing** (`screens/Profile.svelte`): an inline form — display name, a
+  **UTC-offset** timezone dropdown (defaulting to the browser's offset), the away
+  window as hour + 10-minute dropdowns (24-hour, ≤ 12 h), and block toggles — plus an
+  email-binding sub-flow (enter email → enter the confirm code on a numeric field).
+  Invalid fields show a **red border** (no message) and **Save stays disabled** until
+  every field is valid. Interface language stays in **Settings** (it writes through to
+  the account for durable users).
+- **Friend code**: the issued code sits next to a 📋 copy control; tapping the code or
+  the icon copies it. Flex text inputs carry `min-width:0` so they shrink instead of
+  overflowing in Safari.
 - **History / GCG**: the in-game slide-down history gains the running total per move;
   *Export GCG* shares or downloads the `.gcg` file and appears only once the game is
   finished.
+- **Finished game**: the board keeps no last-word highlight and no zoom; the menu drops
+  *Check word* and *Drop game*; and the footer (rack + tab bar) is **drawn but inert**
+  (greyed, non-interactive) rather than hidden, so the layout does not jump. Chat
+  send / nudge are the ⬆️ / 🛎️ icons.
 
 ## Caveat