Email reminders via Resend (custom -5/-1 day offsets)

[thomasjv799]

Summary

Add email notifications via Resend for vehicle document expiry reminders. Email uses its own custom schedule — it fires only at -5 days and -1 day before expiry, independent of the existing Discord/Telegram reminder schedule (-7/-3/-1/0/+1/+3/+7/+15/+30). Single-owner (email goes to the owner).

Scope

1. Self-contained Resend sender

• New utils/email.py exposing send_email(to, subject, html, text=None) -> bool.
• POSTs to https://api.resend.com/emails using RESEND_API_KEY.
• Fully self-contained (each repo owns its copy).
• Never blocks or breaks the primary path: wrapped in try/except, failures logged and swallowed, existing Discord/Telegram delivery unaffected.

2. Custom email offsets in the cron sweep

• In cron/reminder_sweep.py, add a separate email offset set [-5, -1] evaluated independently of the existing notify offsets.
• When a document's days-to-expiry equals -5 or -1, send an email to the owner in addition to whatever the normal schedule does.
• Deduplicate email sends the same way reminders are deduped (extend reminder_log, or add an email-specific dedupe, so the same (vehicle, field, expiry_date, offset) email isn't sent twice).

3. Job-run logging (shared ops table)

• The daily sweep writes one row to the shared ops.job_runs table (defined in the OneRingToRuleThemAll weekly-report issue): job name, started/finished, status, error, counts (vehicles checked, reminders sent, emails sent).

Config / env

• RESEND_API_KEY — Resend key.
• EMAIL_FROM — e.g. Pitstop <reminders@yourdomain>.
• OWNER_EMAIL — recipient address for reminder emails.
• Add to .env.example, README, and the cron GitHub Actions secrets.

Out of scope

• Per-user email (this app is single-owner).
• Changing the existing Discord/Telegram reminder schedule.