feat: Adaptive UI & new Chat page

[BrutalCoding]

Still in draft, but anyone is free to check out my progress and give early feedback.

Checklist:

• [x] System: Adaptive interface (desktop/tablet/mobile)
• [x] System: Routing with Flutter's go_router package
• [x] Page: AI Suite, perhaps too early but basically a collection of AI tools
• [ ] Page: Feedback
• [ ] Page: Settings
• [ ] Page: Chat