feat(integrations): move Telegram credentials into the hub

[plombeer31]

Stacked on #328 (which is stacked on #327). Base is feat/integrations-hub, so the diff here is just Telegram. Retarget down the stack as each lands.

What

Telegram becomes the hub's second tenant, so an operator setting up a new install has one place to paste every key rather than needing to know which service happens to own a tab.

Scope: the credential only

Pairing, the owner id, start/stop and the live chat view stay on the Telegram tab. Those act on a running channel rather than configuring one, and folding a pairing countdown into a credential list would make both surfaces worse.

The hub owns "what is my token"; the tab owns "what is the bot doing". The hub's summary line points at the tab, so the split is discoverable rather than something the operator has to work out.

Validation at entry

The token is checked against the BotFather shape the scrubber already keys off — <6..12 digits>:<≥30 [A-Za-z0-9_-] chars>. A truncated paste stops being a silent "channel won't start" and becomes an immediate, specific complaint about the paste.

Live status

IntegrationStatusContext gains channelStates alongside mcpServerStates, so three states that used to look identical now read differently:

channel	badge	detail
(none / disabled)	configured	token saved — pair and enable on the Telegram tab
up	connected	channel up
down	error	channel failed to start — see the Telegram tab

A merely disabled channel is deliberately not an error — that is a normal resting state, and badging it red would train operators to ignore the badge.

Telegram resolves its token at construction, so it declares appliesLive: false and the pane says a restart is needed rather than leaving the operator to guess why nothing happened.

Testing

npm run lint and npm test green (7211 tests). 6 new tests; every existing Telegram test still passes untouched.

Verified end-to-end against a real runtime:

• hunter2 → refused: "Doesn't look like a bot token — expected digits, a colon, then a long string, as @Botfather issues it." Nothing written.
• a well-formed token → saved, masked as ••••…+13, badge flips to configured with the "pair and enable" detail
• it lands in <stateDir>/.env and is visible in process.env for the Telegram tab's own has-token check, without a restart