fix(reminders): support OAuth SMTP accounts

[RaresKeY]

Summary

Allow email reminders to use a saved Google OAuth SMTP account without a stored SMTP password. Backend account selection now uses the shared SMTP-ready contract, and the Settings reminder selector treats either a saved password or Google OAuth as valid SMTP credentials.

Password accounts and same-owner fallback selection keep their existing behavior. The change is intentionally limited to reminder readiness; SMTP sending remains owned by the existing email transport helper.

Target branch

• This PR targets dev, not main.

Linked Issue

Fixes #5642

Part of #5637

Type of Change

• Bug fix (non-breaking — fixes a confirmed issue)
• New feature (non-breaking — adds new behaviour)
• Breaking change (changes or removes existing behaviour)
• Refactor / cleanup (behaviour unchanged)
• Documentation only
• CI / tooling / configuration

Checklist

• I searched open issues and open PRs — this reminder-specific OAuth readiness bug is not already owned.
• This PR targets dev.
• My changes are limited to reminder account readiness, Settings filtering, and focused tests.
• I ran the app end-to-end. The Settings reminder view was exercised in the running app with synthetic local account data, and browser assertions verified the selected OAuth account. No disposable Google SMTP account was available for live delivery.

How to Test

1. Run:

   python -m pytest -q tests/test_note_reminder_email_oauth.py tests/test_note_reminder_email.py tests/test_email_oauth.py
   node --check static/js/settings.js

2. Save a Google OAuth account with SMTP host/user and no SMTP password.

3. Select it for an email reminder and verify it appears as configured.

4. Dispatch the reminder and verify the shared SMTP helper receives the selected OAuth account.

5. Repeat with a password account and verify existing behavior is unchanged.

Current-dev isolated validation passes 38 focused/adjacent tests, JavaScript syntax, and diff checks. A running-app browser pass also verifies the reminder panel, Email channel, and selected OAuth-only SMTP account. Live SMTP remains a reviewer item.

Visual / UI changes — REQUIRED if you touched anything that renders

The existing reminder account selector can now include Google OAuth SMTP accounts. No layout, style, spacing, or component pattern changed.

• Screenshot or short clip — running-app capture attached below.
• Style match — existing controls and styling are unchanged.
• No new component patterns.
• I am not an LLM agent submitting a bulk PR. Contributor attestation remains for the human author.

Screenshots / clips

Running-app capture using a synthetic local Google OAuth account; no credentials or live provider traffic:

[o3LL]

Approved!
I just want to mention that the How-to-Test command lists tests/test_note_reminder_email.py, which doesn't exist pytest aborts on the missing path, so the command fails as written (the real adjacent suites are test_note_reminder_fire_scope.py etc.).