Fix iOS dark appearance backgrounds

[Ayobami-00]

Summary

Fixes #26.

• Replaces fixed white iOS launch and Flutter host storyboard backgrounds with an adaptive asset-catalog color that matches Tag light/dark app backgrounds.
• Adds regression coverage for native iOS dark appearance resources and first-run system dark appearance in Flutter.

Validation

• flutter analyze
• flutter test
• Targeted simulator/E2E check, if relevant
  • flutter build ios --simulator --debug
  • xcrun ibtool --errors --warnings --notices on LaunchScreen.storyboard and Main.storyboard
  • iOS 26 simulator forced to dark appearance; fresh install launched to first-run onboarding. Sanitized proof uploaded to private demo-proof storage for PR 27 attempt 2.

[greptile-apps]

Greptile Summary

This PR fixes iOS dark mode by replacing hard-coded white backgrounds in LaunchScreen.storyboard and Main.storyboard with a new LaunchBackground named color resolved from a new adaptive asset-catalog colorset (light: #F8F7F2, dark: #0F1115). Regression coverage is added as both a Dart file-system test validating the colorset structure and a Flutter widget test confirming scaffoldBackgroundColor follows the system brightness on first run.

• Asset catalog (LaunchBackground.colorset/Contents.json): two-entry colorset with correct hex values that exactly match the TagTheme dark/light palette.
• Storyboard updates: both storyboards switch to name="LaunchBackground", and LaunchScreen.storyboard gains useTraitCollections="YES" so trait-collection dispatch works for the named color.
• Tests: ios_dark_mode_resources_test.dart checks colorset structure and storyboard content; widget_test.dart adds a dark-appearance scenario with explicit color-value assertions.

Confidence Score: 5/5

Safe to merge — the adaptive color is correctly wired through the asset catalog and both storyboards; the embedded namedColor fallbacks are design-time only and don't affect runtime dark-mode behaviour.

All changed files are iOS resource files and test code. The asset-catalog hex values match the Flutter TagTheme palette exactly. Runtime named-color resolution goes through the asset catalog (which has both variants), so the embedded light-only namedColor in the storyboards is only a design-time concern.

Both storyboard files embed a light-only namedColor fallback; no second look needed for correctness, but IB dark-mode previews will show the wrong colour until the dark appearance entry is added.

Important Files Changed

Filename	Overview
ios/Runner/Assets.xcassets/LaunchBackground.colorset/Contents.json	New adaptive colorset with light (0xF8F7F2) and dark (0x0F1115) variants — hex values match both the storyboard namedColor fallbacks and the Flutter TagTheme palette exactly.
ios/Runner/Base.lproj/LaunchScreen.storyboard	Replaces hard-coded white with name="LaunchBackground" resolved from the asset catalog at runtime; adds useTraitCollections="YES" for trait-collection dispatch. The embedded in resources defines only the light variant, which is a design-time fallback and does not affect runtime dark-mode adaptation.
ios/Runner/Base.lproj/Main.storyboard	Same pattern as LaunchScreen — hard-coded calibratedWhite replaced with the named color reference; embedded fallback is light-only. Already had useTraitCollections="YES" so no attribute change needed.
test/ios_dark_mode_resources_test.dart	New Dart file-system test validating the colorset structure and absence of hard-coded white in both storyboards. Uses _isDefaultColor/firstWhere pattern consistently, and the helper functions are well-scoped.
test/widget_test.dart	Adds a dark-appearance widget test that sets platformBrightnessTestValue before pump, verifies theme.brightness and scaffoldBackgroundColor, and spot-checks two palette colors against constants that match the TagTheme dark palette.

Flowchart

%%{init: {'theme': 'neutral'}}%%
flowchart TD
    A["iOS system trait collection\n(light / dark)"] --> B{"Asset catalog\nnamed-color lookup\ncolorNamed: LaunchBackground"}
    B -->|light| C["#F8F7F2\n(warm off-white)"]
    B -->|dark| D["#0F1115\n(near-black)"]
    C --> E["LaunchScreen.storyboard\nbackgroundColor"]
    D --> E
    C --> F["Main.storyboard\n(Flutter host VC)\nbackgroundColor"]
    D --> F
    E --> G["Launch screen rendered\nby iOS before app code"]
    F --> H["Flutter engine\nmounts on top"]
    I["Storyboard namedColor\nin resources section"] -.->|IB design-time\nfallback only\nlight variant only| E
    I -.->|IB design-time\nfallback only\nlight variant only| F

Loading

_{Reviews (2): Last reviewed commit: "Fix iOS dark appearance backgrounds" | Re-trigger Greptile}