fix(pdf): hand the trip PDF to Safari from the iOS Home Screen app

An iPhone or iPad running TREK from the Home Screen ignores print(), in
the page and in an iframe alike, so "Save as PDF" in the preview did
nothing there. Mobile Safari prints the same preview fine.

In the installed iOS app the preview now shows "Open in Safari" in
place of the dead button, with a line saying why. The link opens the
trip with ?export=pdf, and both shells open their export dialog or
sheet for it, so the PDF is one tap away once Safari is up. The
parameter is dropped once read and survives the login redirect.
Everywhere else the preview prints as before.

The preview overlay moves out of TripPDF.tsx into pdfPreview.ts, which
TripPDF had no room left for under lint:size, and its backdrop and
stacking now use the --overlay and --z-modal tokens.

client/scripts/rtl-baseline.json

@@ -34,7 +34,7 @@
   "components/Map/locationMarkerMapbox.ts": 2,
   "components/Map/nightPauseMarker.ts": 4,
   "components/Map/ratingBadge.ts": 1,
-  "components/PDF/TripPDF.tsx": 8,
+  "components/PDF/TripPDF.tsx": 7,
   "components/PDF/tripMapImage.ts": 1,
   "components/Packing/PackingListPanelBagCard.tsx": 1,
   "components/Packing/PackingListPanelCategoryGroup.tsx": 3,

client/scripts/size-baseline.json

@@ -8,7 +8,6 @@
   "src/components/Map/MapView.tsx": 1385,
   "src/components/Map/MapViewGL.test.tsx": 2919,
   "src/components/Map/MapViewGL.tsx": 2218,
-  "src/components/PDF/TripPDF.tsx": 1039,
   "src/components/Planner/DayDetailPanel.test.tsx": 2333,
   "src/components/Planner/DayPlanSidebar.test.tsx": 5349,
   "src/components/Planner/DayPlanSidebar.tsx": 2929,

client/scripts/theme-baseline.json

@@ -71,7 +71,7 @@
   "components/Map/poiCategories.ts": 7,
   "components/Map/ratingBadge.ts": 2,
   "components/Map/reservationsMapbox.ts": 1,
-  "components/PDF/TripPDF.tsx": 53,
+  "components/PDF/TripPDF.tsx": 51,
   "components/Packing/PackingListPanelBagModal.tsx": 2,
   "components/Packing/PackingListPanelCategoryGroup.tsx": 5,
   "components/Packing/PackingListPanelHeader.tsx": 5,