docs: update README with companion app setup, WebSocket, and new env vars

[thenotespublisher]

README is outdated after today's commits (companion app, DB, WebSocket).

Changes:

• Added section: "Android Companion App" with build instructions (Kotlin, minSdk 26)
• Documented new .env vars: DATABASE_URL (optional SQLite), WS_PORT
• Explained dashboard connection flow (phone → ws://IP:port)
• Added troubleshooting: "Accessibility permission denied" → grant steps
• Fixed broken links, refreshed feature list (now 22→ actions unchanged, but + Android service)

Before/after screenshots attached if you want (optional but helps).

Tested: instructions work on fresh clone + Railway deploy

[manuelpaulo]

True. Mainly: With AND without "Android Companion App", very different build and setting instructions.

[mahijiki1989]

kaise use karen bhai please iska ek youtube video bana kar daalo bhai