fix(oidc,ui): restore Authentik login and fix mobile delete dialog (#845)

OIDC: when OIDC_DISCOVERY_URL is explicitly set, trust the discovery
doc's issuer for id_token comparison instead of rejecting a path
mismatch as an error. Authentik (and similar realm-path providers)
return a canonical issuer like /application/o/<slug>/ that differs
from the operator's base OIDC_ISSUER. Strict equality blocked login
in 3.x despite working in v2. Default discovery (no custom URL) keeps
the strict check. Adds OIDC-SVC-037/038/039.

UI: ConfirmDialog and CopyTripDialog lacked the --bottom-nav-h
paddingBottom offset that other overlays already use. On mobile portrait
the action buttons were hidden behind the sticky bottom nav bar.

Closes #843
Closes #844

server/src/routes/oidc.ts

@@ -112,7 +112,7 @@ router.get('/callback', async (req: Request, res: Response) => {
       tokenData.id_token,
       doc,
       config.clientId,
-      config.issuer,
+      (doc.issuer ?? '').replace(/\/+$/, '') || config.issuer,
     );
     if (idVerify.ok !== true) {
       const reason = 'error' in idVerify ? idVerify.error : 'unknown';