Swap app icon to the v3 design (record button + transcript mic)

- new icon source in icon/ (make_icon_v3.py + masters): near-black
  gradient tile, red record button with white bezel, mic capsule as a
  transcript card with red lines and a cursor
- Android: adaptive icon uses the 512px master as the full-bleed
  background layer (launcher masks crop it to shape) with a transparent
  foreground; old vector foreground and launcher color removed
- desktop: hicolor PNGs replaced at 32-512 px (48 regenerated from the
  master), old SVG removed; install.sh picks them up unchanged
- APK installed on the Fairphone; aapt2 confirms the adaptive icon

README.md

@@ -182,7 +182,7 @@ install.sh            install / uninstall into a local prefix
 bin/meetrec           GUI launcher (installed into ~/.local/bin)
 bin/meetrec-cli       CLI launcher (installed into ~/.local/bin)
 share/applications/meetrec.desktop   XDG desktop entry
-share/icons/hicolor/                app icon (SVG + PNG fallbacks)
+share/icons/hicolor/                app icon (PNGs; source: icon/make_icon_v3.py)
 android/              native Android app (Kotlin + whisper.cpp JNI)
 ```