Feature/decouple poll scheduler

[0xC0FEBABE]

extract pollCreation service to decouple scheduler from poll

officePollSchedule imported startPoll from poll.ts, pulling in SSE,
auth, and email transitively — placing it at layer 6 despite being a
pure scheduling service. Extract creation logic, validation, timers,
and formatPoll into pollCreation.ts (layer 2). The scheduler now
imports createPollRecord directly; poll.ts registers endPoll as the
expiry callback. Drops officePollSchedule from layer 6 to layer 4.

Co-Authored-By: Claude Opus 4.6 noreply@anthropic.com

[TKlerx]

Blocking regression: scheduled polls no longer emit poll_started or send the poll-start email. In src/server/services/officePollSchedule.ts the scheduler now calls createPollRecord directly, which only validates/creates/schedules the poll. The broadcast/email side effects still live in startPoll (src/server/services/poll.ts), so browsers already connected over SSE will stay in the old phase until reconnect/refresh, despite specs/poll-lifecycle requiring poll_started for new active polls. Keep the low-layer creation helper, but have the scheduler trigger the same notification/broadcast path via a small exported wrapper/hook, or otherwise emit poll_started after createPollRecord.

[TKlerx]

Fix verified: scheduled poll creation now calls the shared poll-start announcement hook, preserving SSE poll_started and email notification behavior while keeping pollCreation decoupled from SSE/email imports. Focused scheduler test and precommit validation passed locally.