fix(accesskey): fall back to raster logo when vector rasterization fails

[bmc08gt]

Problem

Drawable.toBitmap on the vector access-key logo crashes on some budget OEM
devices (e.g. Infinix X693, Vortex JK68) with
java.lang.IllegalArgumentException: width and height must be > 0, seen
unhandled in production (Bugsnag 6a47a1e0, and the same signature across
several sibling groups).

Deobfuscating the R8-mapped stack for the crashing build put the failure in
BaseAccessKeyViewModel.createBitmapForExport — specifically the R8-inlined
DrawableKt.toBitmap on ic_flipcash_logo. The logo is a tiny 92×132 bitmap,
so this is not memory pressure. Our dimensions are valid positive
constants; the > 0 violation originates inside VectorDrawable's internal
cache-bitmap allocation on these ROMs — a device-level defect in the
vector→bitmap path.

Fix

• Add a pre-rasterized PNG fallback (ic_flipcash_logo_raster, a
  drawable-nodpi asset reconstructed 1:1 from the vector geometry). It's a
  BitmapDrawable, so toBitmap takes the createScaledBitmap decode/scale
  path and never touches the VectorDrawable cache that crashes.
• Flow: try the vector → on failure recoverCatching with the PNG → if even
  that fails, render the recovery image without the logo (key words + QR
  still intact) and report a non-fatal, instead of dropping the whole image.
• Remove the !! on the logo drawable (latent NPE).

This complements #1027 (which catches the crash but discards the entire image);
here the image survives — with the logo on virtually all devices, and without
it only as a last resort.

Verification

• ./gradlew :apps:flipcash:shared:accesskey:compileDebugKotlin — BUILD
  SUCCESSFUL (regenerates R, confirms the new drawable resolves).
• Rendered PNG visually verified to match the Flipcash logo.
• The OEM vector-cache failure can't be reproduced on non-affected hardware, so
  the fallback firing is only observable in the field once shipped; the PNG
  path is structurally immune to the crash regardless.