Replace the default Flutter icon with a stylised cloud

The app shipped the Flutter template's blue F, which said nothing about what it
does and did not match the interface. The launcher icon is now a white cloud on
the same seed blue the app themes itself with, so the two read as one product.

The icon is drawn rather than hand-edited: tool/generate_icon.py renders it from
signed distance fields — a union of three circles and a rounded box — using only
the standard library, so regenerating it needs no image toolchain. The shape's
framing is derived from its own bounding box, which is what keeps it centred;
maintaining the bounds separately from the shape had it drifting off-centre.

Adds the adaptive icon and the Android 13 monochrome layer, which were missing
entirely. The generator frames the cloud against the 72dp the launcher mask
always keeps and adaptive_icon_foreground_inset is 0, so the layer is not shrunk
twice and the icon reads at the same size as its neighbours on a home screen.

Verified on the emulator: the cloud appears in the app drawer and holds its shape
down to 48px. docs/architecture.md records how to regenerate it, including the
flutter_launcher_icons 0.14.4 bug that writes a string into a boolean Xcode
setting and needs reverting by hand afterwards.

Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>

Nuvolari/app/pubspec.yaml

@@ -33,6 +33,11 @@ dev_dependencies:
     sdk: flutter
   flutter_lints: ^6.0.0
 
+  # Fans the two generated sources out to every Android density, the adaptive
+  # icon and the iOS set. Build-time only: it writes files into android/ and
+  # ios/, which are committed, so nothing here ships in the app.
+  flutter_launcher_icons: ^0.14.4
+
 flutter:
   uses-material-design: true
 
@@ -45,3 +50,33 @@ flutter:
     # the app runnable offline with no credentials.
     - assets/mock/
     - assets/mock/frames/
+
+# Launcher icon, generated from the sources that tool/generate_icon.py draws.
+# Re-run after changing them:
+#
+#     python ../tool/generate_icon.py
+#     dart run flutter_launcher_icons
+flutter_launcher_icons:
+  android: true
+  ios: true
+  image_path: assets/icon/icon.png
+
+  # Adaptive icon: the launcher masks the foreground to its own shape, so the
+  # cloud is drawn inside the safe zone and the app blue fills whatever the mask
+  # leaves. Kept identical to ColorScheme.fromSeed in lib/main.dart.
+  adaptive_icon_background: "#1F6FB2"
+  adaptive_icon_foreground: assets/icon/icon_foreground.png
+
+  # The generator already frames the cloud inside the 72dp safe zone. Left at
+  # its default of 16, this would shrink the layer again and the icon would read
+  # noticeably smaller than every other one on the home screen.
+  adaptive_icon_foreground_inset: 0
+
+  # Android 13 themed icons tint the alpha of this layer with the user's
+  # wallpaper palette. The foreground is a flat white silhouette, so its alpha
+  # is already exactly the cloud.
+  adaptive_icon_monochrome: assets/icon/icon_foreground.png
+
+  # iOS rejects an alpha channel in app icons. The source is opaque anyway;
+  # this drops the channel itself.
+  remove_alpha_ios: true