Update self-hosting docs and server auth config

[Uarmagan]

Summary

• Reworked the self-hosting docs into clearer paths for local quickstart, backups, Google Calendar, manual setup, and server hosting
• Added a practical one-domain server guide and tightened backup/restore instructions
• Made SuperTokens use configured public URLs instead of hardcoded localhost values, with tests to cover the new behavior
• Cleaned up a few stale docs and comments around SSE, Webpack, and Google auth flow

Testing

• Backend SuperTokens test suite passed
• Web env constant test passed
• Type-check passed
• Markdown link and whitespace checks passed
• Caddy config example validated
• Local helper behavior was exercised with a simulated health-check override