feat(app): Logs page with recent events and a level filter (#253)

[rowkav09]

Part of #253 (Logs slice).

Adds /logs to the running app:

• the newest events from %LOCALAPPDATA%\nowplaying\logs\nowplaying.log (last 64 KB, up to 200 events), newest first, refreshing every 3 s
• a level filter (everything / warnings and errors / errors only) and a Copy button for what's shown
• Status, Settings and Logs pages link to each other

Privacy: the log already holds only time, level, component, status and a short code. log-tail.js checks each line against that shape again and drops anything else, so a hand-edited log can't put a server address or token on the page. /api/logs is GET/HEAD only and refuses cross-site requests; a read error returns log_unreadable without the path.

Levels use the existing classes: warning and error are orange shades, never red/green. The troubleshooting doc mentions the page.

[github-actions]

/mira pause

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ All tests successful. No failed tests found.

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[rowkav09]

No Mira review (auto-paused). All checks green; merging.