Stage 10: admin console & dictionary ops (complaint review, hot-reload, broadcasts)

Server-rendered admin console in the backend at /_gm (internal/adminconsole),
fronted on the gateway's public listener by Basic-Auth + a verbatim reverse proxy
(mounted on the edge mux below the h2c wrap). A same-origin check guards its POSTs;
no operator identity is tracked. This supersedes the Stage 6 gateway-fronts-
/api/v1/admin model: GATEWAY_ADMIN_ADDR and the backend /api/v1/admin ping are
dropped and gateway/internal/admin is repurposed to the verbatim proxy.

- Complaints: migration 00008 (+ jetgen) adds disposition/resolution_note/
  resolved_at/applied_in_version + the deferred status CHECK; resolution feeds a
  query-derived pending dictionary-change pipeline (marked applied after a reload).
- Dictionary hot-reload: per-version subdir BACKEND_DICT_DIR/<version>/ via the new
  Registry.LoadAvailable; engine.OpenWithVersions restores resident versions on
  restart. Partially addresses TODO-2.
- Broadcasts: a backend Telegram-connector client (internal/connector,
  BACKEND_CONNECTOR_ADDR) for SendToUser / SendToGameChannel (discharges the Stage 9
  forward-note).
- Admin reads: account.ListAccounts/CountAccounts/Identities and
  game.ListGames/CountGames/GameByID/ListComplaints/GetComplaint/CountComplaints/
  ResolveComplaint/DictionaryChanges/MarkChangesApplied.
- Tests: adminconsole render, engine reload, same-origin guard, gateway verbatim
  proxy + h2c console mount, inttest complaint pipeline + list/count + /_gm console.
- Docs: PLAN (Stage 10 done + refinements + TODO-2), ARCHITECTURE §1/§5/§6/§12/§13,
  FUNCTIONAL (+_ru), TESTING, backend/gateway READMEs.

backend/internal/connector/client.go

@@ -0,0 +1,58 @@
+// Package connector is the backend's gRPC client for the Telegram platform
+// connector side-service. The admin console uses it to send operator broadcasts:
+// a direct message to one user, or a post to the connector's configured game
+// channel. The connector lives on the trusted internal network, so the
+// connection uses insecure (plaintext) transport credentials
+// (docs/ARCHITECTURE.md §12). It mirrors gateway/internal/connector, narrowed to
+// the two broadcast methods the admin surface needs.
+package connector
+
+import (
+	"context"
+	"fmt"
+
+	"google.golang.org/grpc"
+	"google.golang.org/grpc/credentials/insecure"
+
+	telegramv1 "scrabble/pkg/proto/telegram/v1"
+)
+
+// Client wraps the connector's Telegram gRPC service.
+type Client struct {
+	conn *grpc.ClientConn
+	c    telegramv1.TelegramClient
+}
+
+// New dials the connector gRPC endpoint at addr.
+func New(addr string) (*Client, error) {
+	conn, err := grpc.NewClient(addr, grpc.WithTransportCredentials(insecure.NewCredentials()))
+	if err != nil {
+		return nil, fmt.Errorf("connector: dial %s: %w", addr, err)
+	}
+	return &Client{conn: conn, c: telegramv1.NewTelegramClient(conn)}, nil
+}
+
+// Close releases the gRPC connection.
+func (c *Client) Close() error { return c.conn.Close() }
+
+// SendToUser sends an operator text message to one user, addressed by their
+// platform external_id. delivered reports whether the connector actually sent it
+// (false when the user has not started the bot).
+func (c *Client) SendToUser(ctx context.Context, externalID, text string) (bool, error) {
+	resp, err := c.c.SendToUser(ctx, &telegramv1.SendToUserRequest{ExternalId: externalID, Text: text})
+	if err != nil {
+		return false, err
+	}
+	return resp.GetDelivered(), nil
+}
+
+// SendToGameChannel posts an operator text message to the connector's configured
+// game channel. delivered reports whether the connector sent it (false when no
+// channel is configured).
+func (c *Client) SendToGameChannel(ctx context.Context, text string) (bool, error) {
+	resp, err := c.c.SendToGameChannel(ctx, &telegramv1.SendToGameChannelRequest{Text: text})
+	if err != nil {
+		return false, err
+	}
+	return resp.GetDelivered(), nil
+}