Store OIDC code_verifier and state in sessionStorage instead of
static memory variables. This fixes the "No code verifier" error
that occurred after Authentik redirect because the Flutter app
restarts and loses in-memory state.
🤖 Generated with [Claude Code](https://claude.com/claude-code)
Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>
Web authentication now uses OIDC Authorization Code flow with PKCE
instead of NPM forward auth. Added callback route and web utilities.
🤖 Generated with [Claude Code](https://claude.com/claude-code)
Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>