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#843Closes#844
Introduces CopyTripDialog — a two-section modal that appears before the
copy action and lists what is carried over (days, places, budget items,
packing lists, TODOs, notes) and what is intentionally skipped
(collaborators, collab data, files, share tokens). Addresses the UX gap
raised in #786.