Fix migration connection exhaustion and polish auth pages
- apply-migrations.ts: use single shared connection instead of one per operation
- Increase MariaDB max_connections from 151 to 300 in server config
- home-login-form.tsx: replace hardcoded gray colors with theme variables
- register-form.tsx: add password strength meter, spinner, theme-aligned inputs
- login-form.tsx: add Discord/Google SVG icons, spinner, smoother 2FA animation
- page/register/login: apply premium animations (float, stagger, glow, gradient)