R1: schema & naming reset — squash migrations, rename variants

Squash the 12 goose migrations into one 00001_baseline.sql (there is no prod
data; verified schema-identical to the chain via a pg_dump diff + the green
integration suite) and rename the game-variant labels
english/russian_scrabble/erudit -> scrabble_en/scrabble_ru/erudit_ru across the
backend, the FlatBuffers wire values and the UI.

dawg filenames and the Go enum identifiers are unchanged; the i18n display keys
are kept. Adds PRERELEASE.md (the R1-R7 pre-release tracker), linked from
CLAUDE.md. Contour DB wipe and the scrabble-dictionary tidy are follow-ups.

backend/README.md

@@ -71,18 +71,18 @@ gateway. Stage 9 adds the gateway-only `POST /api/v1/internal/push-target` (a us
 Telegram `external_id`, language and `notifications_in_app_only` flag) that the gateway
 uses to route out-of-app push to the Telegram connector, extends the Telegram login to
 seed a new account's language and display name from the launch fields, and adds
-migration `00007` (`accounts.notifications_in_app_only`, default true).
-Migration `00005` adds `accounts.is_guest`: an ephemeral guest is a durable row
+the `accounts.notifications_in_app_only` flag (default true).
+`accounts.is_guest` marks an ephemeral guest — a durable row
 with no identity, excluded from statistics. **Stage 10** adds the server-rendered
 **admin console** at `/_gm` (`internal/adminconsole` + `internal/server/handlers_admin_console.go`;
 the gateway fronts it with Basic-Auth and a same-origin guard protects its POSTs), the
-**complaint resolution** lifecycle (migration `00008` adds `disposition`/`resolution_note`/
-`resolved_at`/`applied_in_version` + the `status` CHECK) feeding a dictionary-change
+**complaint resolution** lifecycle (the `complaints` `disposition`/`resolution_note`/
+`resolved_at`/`applied_in_version` columns + the `status` CHECK) feeding a dictionary-change
 pipeline, dictionary **hot-reload** from `BACKEND_DICT_DIR/<version>/`
 (`engine.OpenWithVersions` / `Registry.LoadAvailable`), and operator **broadcasts** via a
 backend Telegram-connector client (`internal/connector`, `BACKEND_CONNECTOR_ADDR`) — each
 broadcast picks the delivering bot by an operator-chosen language. **Stage 15** adds
-migration `00010` (`accounts.service_language`): the language tag of the bot a Telegram
+`accounts.service_language`: the language tag of the bot a Telegram
 user last signed in through, written on every login and returned by
 `/internal/push-target` (falling back to `preferred_language`) so out-of-app push routes
 to the right bot. The shared wire contracts live in the sibling [`../pkg`](../pkg) module.
@@ -96,7 +96,7 @@ friends/blocks de-duplicated, the secondary kept as a `merged_into` tombstone (s
 shared finished game's foreign keys hold); a shared **active** game blocks the merge.
 The current account is primary, except a guest initiator whose linked identity has a
 durable owner — then the durable account wins and a fresh session is minted for it.
-Migration `00009` adds `paid_account`/`merged_into`/`merged_at`. This supersedes the
+The `accounts.paid_account`/`merged_into`/`merged_at` columns back this. This supersedes the
 Stage 8 `email.bind.*` edge surface (the `RequestCode`/`ConfirmCode` primitives stay).
 
 ## Package layout
@@ -176,7 +176,10 @@ warmed.
 ## Migrations & generated code
 
 Migrations are plain goose SQL under `internal/postgres/migrations` (sequential
-`NNNNN_name.sql`), embedded and applied at startup. After changing the schema,
+`NNNNN_name.sql`), embedded and applied at startup. The incremental history was
+squashed into a single `00001_baseline.sql` before the first production deploy
+(there was no production data); new schema changes append as `00002_*` onward.
+After changing the schema,
 regenerate the committed go-jet code (needs Docker):
 
 ```sh