feat(telegram): split connector into home validator + remote bot

Move all Telegram egress off the main host. The single connector held the
bot token, long-polled Telegram and answered the gateway/backend over the
trusted internal network, so the whole component (including login validation)
shared fate with its VPN sidecar. Split it into two binaries that share the
token:

- cmd/validator (home, no VPN): Mini App initData + Login Widget HMAC only,
  never calls the Bot API. The gateway dials it for Telegram auth, so game
  login is now independent of Telegram reachability.
- cmd/bot (remote): Bot API long-poll + sendMessage, the only component
  reaching Telegram. It holds no inbound port — it dials the gateway over a
  new reverse mTLS bot-link (pkg/proto/botlink/v1) and executes the send
  commands the gateway pushes.

The gateway funnels sends to the bot-link: out-of-app push is fire-and-forget
(at-most-once, dropped if no bot is connected); the backend admin broadcasts
reach a gateway-served relay that forwards them and awaits the bot's ack
(SendToUser/SendToGameChannel contract preserved). mTLS (pkg/mtls) is the one
inter-service link that leaves the trusted segment; validator<->gateway and
the relay stay plaintext internal. The bot is Telegram-rate-limited.

One bot now; the gateway bot registry, an owns_updates flag and per-command
ids leave seams for N later. Webhook rejected (one URL per token, adds inbound
+ a static address).

The unified test contour runs the split (the bot keeps its VPN sidecar and
dials the gateway by its internal name; bot-link certs from deploy/gen-certs.sh,
generated in CI). The prod wiring — the bot on a separate host (no VPN), the
gateway bot-link port published, PROD_ certs with scheduled rotation, an SSH
deploy of both hosts together — is the deferred final stage (PRERELEASE.md TX,
Stage 18).

Docs: ARCHITECTURE, PRERELEASE (phase TX), platform/telegram + gateway +
backend + deploy READMEs, FUNCTIONAL(+ru), CLAUDE.md, .env.example.

backend/internal/connector/client.go

@@ -1,10 +1,10 @@
-// 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 game channel, through the single
-// bot. 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 is the backend's gRPC client for operator broadcasts: a direct
+// message to one user, or a post to the game channel. It calls the gateway's
+// bot-link relay (which forwards the send to the remote bot over the reverse mTLS
+// link and reports back whether it was delivered). The relay lives on the trusted
+// internal network, so the connection uses insecure (plaintext) transport
+// credentials (docs/ARCHITECTURE.md §12). It speaks the Telegram service contract,
+// narrowed to the two broadcast methods the admin surface needs.
 package connector
 
 import (