feat: add realtime 2027 job feed packets

[eyesofish]

What changed

• Added realtime monitoring for the selected 2027 US internship and new-grad aggregate feeds.
• Added work-authorization filtering, canonical deduplication, employer-JD retrieval, durable queue state, and Persona-based application packet generation.
• Added application packet exports, ready-to-apply dashboard handoff, Gmail notifications, operational APIs, settings, and Docker persistence.
• Added explicit 09:00 and 20:30 Asia/Shanghai SpeedyApply schedules while retaining the higher-frequency aggregate feed poller.
• Added focused regression coverage and implementation documentation.

Why

The existing project could discover jobs and tailor resumes interactively, but it did not provide a durable end-to-end handoff for newly published 2027 US roles. This change adds a restart-safe pipeline from source detection through a locally reviewable application packet while keeping final employer form submission manual.

User and developer impact

Users can monitor selected feeds, review filtered jobs in Job Feed, and receive a mapped resume packet plus direct application URL. Operators must keep the backend running, populate Persona, configure an LLM, and reauthorize Gmail with send scope if notifications are desired.

Validation

• python -m pytest -q — 496 passed
• npm run build — production build succeeded
• git diff --cached --check — passed before commit