feat: Scalar API docs, community health files, Quickstart cards (#41)

* feat: Scalar API docs, community health files, Quickstart cards, GHCR Docker

Backend:
- Replace Swagger UI with Scalar at /docs (scalar-fastapi)
- Add OpenAI-compatible /v1/audio endpoints (openai_compat router)
- Add TTS streaming endpoint (tts_stream router)
- Add voice marketplace router (marketplace)
- Update TTS backend registry

Frontend:
- Refine CaptureWidget, WaveformTimeline, App layout
- CSS polish and index.css updates

Community health:
- SECURITY.md — vulnerability reporting policy
- CODE_OF_CONDUCT.md — Contributor Covenant v2.1
- .github/FUNDING.yml — GitHub Sponsors
- .github/ISSUE_TEMPLATE/ — bug report + feature request
- .github/pull_request_template.md — PR checklist

README:
- Quickstart redesigned as 3-column progressive cards
- Docker section updated with GHCR pull instructions
- API Docs row added to service table

Infra:
- scalar-fastapi added to pyproject.toml + uv.lock
- research/ added to .gitignore

* refactor: clean up documentation and logging while enhancing desktop packaging dependencies and capture UI performance.

* fix: address CodeRabbit review — streaming, escaping, thresholds

Backend:
- marketplace: stream zip entries via ZipFile.open()/copyfileobj, add 100MB
  upload cap, fix raise-from exception chaining (OOM prevention)
- openai_compat: _encode_audio returns actual file ext so Content-Disposition
  matches real format; forward non-profile voices when DB row not found
- tts_stream: send 'start' frame after generation so sample_rate is real;
  forward non-profile voices on DB miss
- capture_ws: split MIN_BUFFER_BYTES into separate partial/final thresholds
  so short utterances (<2s) still get transcribed

Frontend (Tauri):
- lib.rs: tray 'dictate' now toggles start/stop based on widget visibility
- commands.rs: XML-escape exe path in LaunchAgent plist, shell-quote in
  .desktop Exec line to prevent injection from special-char paths
- CaptureWidget.css: fix Stylelint violations (empty lines, font-family quotes)

.gitignore

@@ -84,3 +84,4 @@ test-results/
 
 # Research repos (local only)
 research/
+marketing.md