feat: LUKS2 encryption, boot sequence fixes, onboarding auth, CI/CD

- LUKS2 full-partition encryption for /var/lib/archipelago/ (TASK-42)
  4-partition layout: BIOS + EFI + root (30GB) + encrypted data
  AES-256-XTS with AES-NI detection, ChaCha20 fallback for ARM
  Auto-unlock via crypttab + random key file

- Fix EFI boot errors: remove shim-signed, clean shim artifacts
- Fix first-boot sequence: always show boot animation before onboarding
- Fix stale localStorage causing login instead of onboarding (BUG-47)

- Add auth.setup + auth.isSetup RPC handlers for password on clean install
- Add onboarding methods to UNAUTHENTICATED_METHODS (DID sign 403 fix)

- FileBrowser bundled in unbundled ISO, fix auto-login Secure cookie (BUG-46)
- Kiosk mode: xorg/chromium in rootfs, toggle script, MOTD instructions

- Add Gitea Actions CI/CD workflow for automatic ISO builds

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

core/archipelago/src/api/rpc/dispatcher.rs

@@ -16,6 +16,8 @@ impl RpcHandler {
             "auth.login" => self.handle_auth_login(params).await,
             "auth.logout" => self.handle_auth_logout().await,
             "auth.changePassword" => self.handle_auth_change_password(params, session_token).await,
+            "auth.isSetup" => self.handle_auth_is_setup().await,
+            "auth.setup" => self.handle_auth_setup(params).await,
             "auth.onboardingComplete" => self.handle_auth_onboarding_complete().await,
             "auth.isOnboardingComplete" => self.handle_auth_is_onboarding_complete().await,
             "auth.resetOnboarding" => self.handle_auth_reset_onboarding(params).await,