feat(game): finished-game export as a PNG image behind a format chooser

The history header's export button now opens a chooser — Telegram's
native popup inside Telegram, the app's own modal elsewhere — offering
the GCG file and a new client-rendered PNG of the final position
(lib/gameimage, Canvas 2D, lazy dynamic import, zero dependencies):
light theme, classic A..O/1..15 axes, label-free premium fills, and a
fixed-typography per-seat scoresheet with GCG-style move coordinates,
multi-word sub-lines, endgame rack-settlement row, winner trophy and a
hostname + device-locale finish date footer; a long game stretches the
board, never the typography.

Delivery mirrors the GCG rules (Web Share with no blob fallback, else
download) except on Android Telegram/VK WebViews and the desktop VK
iframe, where a binary PNG has no clipboard-text fallback: those get a
preview modal with a long-press/right-click save hint and a copy-image
button where ClipboardItem exists.

docs/FUNCTIONAL.md

@@ -16,7 +16,7 @@ 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. It also handles 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.
+email, the statistics screen, and the in-game history viewer with GCG / PNG-image 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.
@@ -318,12 +318,35 @@ silently ignores their messages) or clear a thread's messages. This is independe
 Feedback above — it serves people who write to the bot directly rather than through the app.
 
 ### History & statistics
-Finished games are archived in a dictionary-independent form and exportable to
-GCG; the export is offered **only once a game is finished**, and never for an
-honest-AI practice game (a live game's export would leak the move journal; an AI
-game is throwaway). The client shares the `.gcg` file where the platform supports
-it; on an Android in-app client (Telegram / VK), which has neither Web Share nor a working file
-download, it copies the GCG to the clipboard (with a confirming toast); otherwise it downloads the file. Statistics (durable accounts only):
+Finished games are archived in a dictionary-independent form and exportable in
+**two formats behind one 📤 button** — the GCG file and a rendered **PNG image** of
+the final position; the export is offered **only once a game is finished**, and
+never for an honest-AI practice game (a live game's export would leak the move
+journal; an AI game is throwaway). The format chooser is native where the platform
+has one (Telegram's popup), the app's own modal elsewhere.
+
+The **image** is rendered on the client (Canvas 2D, always the light theme): the
+final board with classic coordinate axes A..O / 1..15 on the left — premium squares
+as plain colour fills, no text labels — and a compact per-seat scoresheet on the
+right: each seat's name and final score in the header (🏆 by the winner), then one
+row per move carrying the main word's classic coordinate (an across play is
+row-first, `8G`; a down play column-first, `H8` — the GCG convention), the word and
+its points; extra words of a multi-word play ride a smaller second line, non-play
+moves show as localized notes (pass/exchange/resign/timeout), and a closing ± row
+shows the endgame rack settlement when there was one (the final scores are
+authoritative — running totals alone do not include it). The footer stamps the site
+host and the finish date in the device locale. The scoresheet typography is fixed;
+a long game stretches the board (never below its minimum) so the image carries no
+dead space.
+
+Delivery per format: the **GCG** file is Web-Shared where the platform supports it;
+on an Android in-app client (Telegram / VK), which has neither Web Share nor a
+working file download, it copies the GCG text to the clipboard (with a confirming
+toast); otherwise it downloads the file. The **PNG** shares or downloads the same
+way where possible, but a binary image has no clipboard-text fallback — those
+in-app webviews (and the desktop VK iframe) get a **preview modal** instead: the
+image with a long-press / right-click save hint and a copy-image button where the
+clipboard-image API exists. 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). It
 also shows the player's **move count** (their plays — passes and exchanges do not