Fix(auth): migrate to modern Supabase SSR cookie/session methods, resolve all auth/session issues that could lead to random logouts.

• Migrated all API/auth/middleware to use Supabase SSR getAll/setAll cookie methods

• Ensured secure cookie options (httpOnly, secure, sameSite, path) everywhere

• Fixed PKCE OAuth flow: code_verifier cookie is now reliably stored/retrieved

• Magic link login bug fixed (no longer requires unused 'type' field)

• Default redirect to /dashboard after login if no next param

• Removed all legacy/unused Supabase client code

• No deprecated cookie methods or TODOs remain

• Codebase is now robust, secure, and production-ready for authentication

BREAKING CHANGE: Legacy Supabase client/server utils removed, all routes must use new SSR cookie API