Support HTTPS via self-signed certificate for local network

[Aaryan2R]

Problem

HomeVault currently runs over HTTP only. Browsers show a "Not Secure" warning which concerns users and blocks some browser features (like clipboard access, which requires HTTPS).

Solution

Add optional HTTPS support using a self-signed certificate:

1. Generate a self-signed cert with Python (cryptography library)
2. Pass ssl_context to Flask or configure Nginx to serve HTTPS
3. Add a setup option to enable/disable HTTPS

Notes

• Cloudflare Tunnel (planned for v1.3) will handle remote HTTPS automatically
• This issue is specifically for local network HTTPS
• Users will need to accept the browser security warning once for self-signed certs
• Cert generation should be automatic during setup