feat(sun-position): add proportional arc visualization with 10-min updates

- Arc angle now proportional to day/night duration (day = daylight/24 × 360°)
- Horizon points represent sunrise/sunset times
- Day arc with sun icon and yellow/orange gradient
- Night arc with moon icon and blue/indigo gradient
- Position updates every 10 minutes aligned to clock (0/10/20/30/40/50)
- Default to 07:00-17:00 when API data unavailable (asymmetric for visual effect)
- All environment cards maintain consistent height in "no data" state

🤖 Generated with [Claude Code](https://claude.com/claude-code)

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

pubspec.yaml

@@ -16,7 +16,7 @@ publish_to: 'none' # Remove this line if you wish to publish to pub.dev
 # https://developer.apple.com/library/archive/documentation/General/Reference/InfoPlistKeyReference/Articles/CoreFoundationKeys.html
 # In Windows, build-name is used as the major, minor, and patch parts
 # of the product and file versions while build-number is used as the build suffix.
-version: 1.5.1+1
+version: 1.5.2+1
 
 environment:
   sdk: ^3.10.4