docs: final 1.0.0 documentation pass

README.md:
- Node prerequisite: v12+ → v22+
- Real-Time Updates: describe SSE push, remove polling/refresh-selector wording
- On-demand mode: update for SSE connect triggering poll
- API Endpoints: add /stream, /me, /csrf, /user-summary, /status, /cover-art
- Remove stale /api/qbittorrent proxy entry
- Docker tags: update to 1.0.x

SECURITY.md:
- Supported versions: add 1.0.x, retire 0.2.x
- CSP header: add style-src-attr 'unsafe-inline'
- Nginx example: add proxy_buffering off / proxy_read_timeout for SSE

Diagrams:
- seq-dashboard.puml: rewrite as SSE stream sequence (connect,
  initial payload, pushed updates, heartbeat, disconnect)
- seq-polling.puml: add SSE subscriber notification step after
  cache population
- state-ui.puml: replace Refresh Rate sub-state with SSE Connection
  state machine; update splash loading and logout transitions
- state-poller.puml: add Notifying SSE subscribers step in Polling state

package.json: bump to 1.0.0

package.json

@@ -1,6 +1,6 @@
 {
   "name": "sofarr",
-  "version": "0.2.0",
+  "version": "1.0.0",
   "description": "A personal media download dashboard that shows your downloads 'so far' while you relax on the sofa waiting for your *arr services to finish",
   "main": "server/index.js",
   "scripts": {