Stage 0: scaffold monorepo, backend skeleton, docs, CI

- go.work (Go 1.26.3) with backend module; deps added incrementally (gin+zap only)

- backend: /healthz + /readyz, env config, graceful shutdown

- docs: ARCHITECTURE, FUNCTIONAL (+ru mirror), TESTING

- PLAN.md (stage tracker + per-stage open details) and CLAUDE.md (per-stage workflow)

- .gitea go-unit CI (gofmt/vet/build/test)

docs/FUNCTIONAL.md

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+# Scrabble Game — Functional spec
+
+Per-domain user stories: what each user-visible operation does. This is the
+starting point for any change request that touches behaviour. The English
+version is authoritative; [`FUNCTIONAL_ru.md`](FUNCTIONAL_ru.md) is a mirror for
+the project owner — mirror every point edit in the same patch (translate only
+the changed paragraphs). Sections deepen as stages land; *(Stage N)* marks where
+the detail is authored.
+
+## Domains
+
+### Identity & sessions *(Stage 1 / 6)*
+A player arrives from a platform (Telegram first), via email login, or as an
+ephemeral guest. The gateway validates the credential once and mints a thin
+session token; the backend resolves it to an internal `user_id`. Guests are
+session-only with restricted features (auto-match only; no friends, stats or
+history).
+
+### Accounts, linking & merge *(Stage 1 / 10)*
+First platform contact auto-provisions a durable account. From the profile a
+player links additional platform identities or an email via a confirm flow;
+linking an identity that already has history merges it into the current
+account (stats summed, games/friends transferred).
+
+### Lobby & matchmaking *(Stage 4)*
+Bottom tab menu: **my games**, **profile**. Auto-match (always 2 players) joins
+a `(variant, language)` pool; after 10 s with no human, the robot substitutes.
+Friend games (2–4) are formed by friend list, internal ID, or deep-link.
+
+### Playing a game *(Stage 3)*
+Place tiles, pass, exchange, or resign. A play is validated against the
+dictionary at submit time and scored. One hint per game reveals the best move.
+The dictionary check tool is unlimited and offers a complaint. The game ends
+when the bag empties and a player clears their rack, after 6 consecutive
+scoreless turns, or by the 24-hour move timeout (auto-resign).
+
+### Robot opponent *(Stage 5)*
+Indistinguishable-from-human substitute in auto-match. Decides once whether to
+play to win (~40%), targets a small score margin, plays with human-like timing
+and a night sleep window, and nudges/answers nudges like a person.
+
+### Social: friends, block, chat, nudge *(Stage 4)*
+Add friends; block chat and/or friend requests independently; per-game chat;
+nudge the awaited opponent at most once per hour (platform-native push).
+
+### Profile & settings *(Stage 4)*
+Language (en/ru), display name, linked accounts, email binding, timezone, block
+toggles.
+
+### History & statistics *(Stage 3)*
+Finished games are archived in a dictionary-independent form and exportable to
+GCG. Statistics: wins, losses, max points in a game, max points for one word.
+
+### Administration *(Stage 9)*
+Admin (Basic Auth at the gateway) reviews word complaints, manages dictionary
+versions, and inspects users/games.