Stage 8: UI social/account/history surfaces

Wire the deferred Stage 7 surfaces end-to-end (UI -> gateway transcode ->
backend REST -> existing domain services): friends (incl. one-time friend
codes), per-user blocks, friend-game invitations, profile editing + email
binding, the statistics screen, and the in-game history + GCG export.

Friends gain two add paths (interview decision, a deliberate plan change):
one-time 6-digit codes (friend_codes table, 12h TTL, single-use, rate-limited
redeem); and play-gated requests (shared game required) where an explicit
decline is permanent, an ignored request lapses after 30 days, and a code
bypasses a decline. Migration 00006 widens friendships_status_chk and adds
friend_codes.

Lobby notification badge is poll + push: a new generic `notify` event drives
it live; the client polls on open/focus. Language stays a single Settings
control that writes through to the durable account's preferred_language. GCG
export is finished-only (game.ErrGameActive) and shares/downloads the .gcg file.

Tests: backend unit + inttest (friend gate/decline/code, ListInvitations,
GetStats, GCG gate), gateway transcode round-trips + notify constructor, UI
vitest (codecs, win-rate, share choice) + Playwright social specs. Docs: PLAN
(Stage 8 done + refinements + TODO-5), ARCHITECTURE, FUNCTIONAL(+ru), UI_DESIGN,
TESTING, module READMEs.

docs/FUNCTIONAL.md

@@ -15,10 +15,10 @@ The web/app client (Svelte + Vite) realizes these stories. The **playable slice*
 auto-match, playing the board (place tiles by drag or tap, pass, exchange, resign),
 the top-1 hint, the unlimited word-check with complaint, per-game chat and nudge,
 real-time in-app updates, switching interface language (en/ru) and theme, and a
-read-only profile. Managing friends and blocks, creating friend games (invitations),
-editing the profile, the statistics screen and the history/GCG viewer arrive in
-Stage 8. Settings also pick the board's bonus-label style (beginner / classic /
-none). A hint **lays the suggested tiles on the board** for the player to confirm and
+read-only profile. **Stage 8** adds managing friends (including one-time friend
+codes) and blocks, friend-game invitations, editing the profile and binding an
+email, the statistics screen, and the in-game history viewer with GCG export.
+Settings also pick the board's bonus-label style (beginner / classic / none). A hint **lays the suggested tiles on the board** for the player to confirm and
 costs nothing when the rack has no legal move. The word-check accepts only the
 variant's alphabet, remembers answers within the session and rate-limits repeats.
 
@@ -42,10 +42,10 @@ account (stats summed, games/friends transferred).
 Bottom tab menu: **my games**, **profile**. Auto-match (always 2 players) joins a
 per-variant pool and is paired with the next waiting human; after 10 s with no
 human the robot substitutes (the robot arrives in Stage 5). Friend games (2–4) are
-formed by inviting players from the friend list or by internal ID (deep-link
-invites arrive with the platform integration): the inviter chooses the settings
-and the game starts once every invitee has accepted — any decline cancels it, and
-an unanswered invitation expires after seven days.
+formed by inviting players from the friend list (deep-link invites arrive with the
+platform integration): the inviter chooses the settings and the game starts once
+every invitee has accepted — any decline cancels it, and an unanswered invitation
+expires after seven days.
 
 ### Playing a game *(Stage 3)*
 Place tiles, pass, exchange, or resign. A play is validated against the game's
@@ -74,9 +74,13 @@ one, and a night-time pause that tracks the player's own day. It answers a nudge
 within a few minutes and nudges back when the player has been away a long time. It
 carries a human-like name and neither chats nor accepts friend requests.
 
-### Social: friends, block, chat, nudge *(Stage 4)*
-Send a friend request and have it accepted (decline or cancel withdraws it,
-unfriending removes the friendship). Block globally — switch off incoming chat
+### Social: friends, block, chat, nudge *(Stage 4 / 8)*
+Become friends in two ways: redeem a **one-time code** the other player issues (six
+digits, valid for twelve hours), or send a **request to someone you have played
+with** — they accept, ignore it (a request lapses after thirty days and can then be
+re-sent), or decline (a decline blocks further requests from you until they hand you
+a code). Cancelling your own pending request withdraws it; unfriending removes the
+friendship. Block globally — switch off incoming chat
 and/or friend requests — and block individual players (a per-user block hides that
 person's chat and stops requests and game invitations both ways; it also ends any
 existing friendship). Per-game chat is for quick reactions: messages are short
@@ -91,11 +95,13 @@ once entered, attaches the email to the account (an email already confirmed by
 another account cannot be taken — that is a merge, a later stage). Linked platform
 accounts and merge arrive in Stage 11.
 
-### History & statistics *(Stage 3)*
+### History & statistics *(Stage 3 / 8)*
 Finished games are archived in a dictionary-independent form and exportable to
-GCG. Statistics (durable accounts only): wins, losses, draws, max points in a
-game, and max points for a single move (the best play, which already includes
-every word it formed plus the all-tiles bonus).
+GCG; the export is offered **only once a game is finished** (exporting a live game
+would leak the move journal), and the client shares the `.gcg` file where the
+platform supports it, otherwise downloads it. Statistics (durable accounts only):
+wins, losses, draws, max points in a game, and max points for a single move (the
+best play, which already includes every word it formed plus the all-tiles bonus).
 
 ### Administration *(Stage 10)*
 Admin (Basic Auth at the gateway) reviews word complaints, manages dictionary