chore(web): extract App.tsx's connection lifecycle into useConnectionLifecycle

Phase 2 step 3 of the App.tsx decomposition (#2154, under #2129/#2126).

Moves the whole connection cluster out of App.tsx and into
clients/web/src/hooks/useConnectionLifecycle.ts: setupClientForServer
(the single place a connection is configured), onToggleConnection,
onDisconnect, onReauthenticateFromBanner, the deep-link auto-connect
effect and its three phase latches, the connected/teardown/disconnect
effects, connectErrorMessage, and the session-scoped reset a disconnect
triggers. Handshake telemetry rides along as useHandshakeTelemetry,
split out only because useOAuthRecovery runs first and stamps the same
ref.

No behavior change. App.tsx goes 3,039 -> 2,412 lines.

Per #2129, resetSessionScopedUiState takes a narrow SessionResetSurface
- one reset() per owner - rather than every phase-1 setter, so the hook
does not end up depending on everything phase 1 extracted. The two
log-level operations stay App-owned because the connect path seeds the
same state.

Closes #2154

Signed-off-by: cliffhall <cliff@futurescale.com>

Author: cliffhall