v0.3: dashboard local mode, openbridge tab reuse, tab activation fix

- dashboard.html: local dashboard.json mode (10s poll) alongside artifact db mode;
  clickable cards behind an http(s)-only safeUrl filter; meta charset; mode-aware
  freshness line
- openbridge.py: localhost shim exposing open_link so dashboard clicks reuse the
  platform's warm tab instead of spawning one per click
- cdp.py: Tab.activate(); get_or_open_tab activates reused tabs — a backgrounded
  tab never finishes rendering, which made YouTube's login check read a signed-in
  account as signed out
- README/MANIFEST: corrected CDP port (9336, was documented as 9222), removed the
  false claim that the server writes dashboard.json, documented the reboot/VPS
  requirements
- .gitignore: __pycache__/, *.pyc, state.json, Archived/; removed stale tracked
  pycache and state.json from index

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