migrate web to next 16 template and redesign landing page (#526)

* migrate web to next-template stack (next 16, react 19, tailwind 4)

replace all infrastructure with next-template conventions:
- next.js 14 -> 16 (turbopack default, typed routes, react compiler)
- react 18 -> 19
- tailwind css 3 -> 4 (css-first config, oklch theme system)
- eslint 8 (.eslintrc) -> 9 (flat config with stricter rules)
- add shadcn/ui, base-ui, cva component primitives
- upgrade theme toggle to light/dark/system dropdown
- migrate hardcoded neutral classes to semantic oklch tokens
- drop unused @tailwindcss/forms, autoprefixer

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

* add no-misused-promises config for async JSX handlers, warn on array index keys

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

* base-vega

* sync frosty web with next-template runtime and claude tooling for cloudflare parity

* gitignore .dev.vars per cloudflare best practice

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

* add observability configuration to wrangler.jsonc

* remove marquee emote background from hero section

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

* improve CLAUDE.md and AGENTS.md files across project

Remove redundant root CLAUDE.md (kept in .claude/ instead), add Commands
and Source Structure sections to Flutter AGENTS.md, clarify global vs
feature store placement, and fill gaps in web AGENTS.md (shadcn base-vega
style, constants.ts, no-array-index-key rule, commit conventions).

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

* switch shadcn theme from neutral to violet, replace twitch-purple with primary token

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

* initial redesign

* auto-infer nativeButton in Button wrapper when render prop is used

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

* replace skeleton carousel with real screenshots and video, add responsive phone scaling and mobile menu

- Replace PhoneSkeleton with PhoneFrame/PhoneMedia using actual app screenshots and video
- Fluid phone sizing via aspect-ratio with responsive max-h/max-w caps
- Non-circular carousel with swipe gestures, dot indicator, and hover opacity boost
- Video plays only when focused, pauses when off-screen
- Collapse header actions into dropdown menu on mobile, add Contact link
- Viewport-height layout with no scrolling on any screen size
- Remove footer, move contact to header

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

* improve header consistency, carousel layout, and responsive centering

- add icons to all header buttons (Contact, Donate, GitHub)
- switch theme toggle to ghost variant for consistency
- bump header collapse breakpoint from md to lg
- move carousel arrows to overlay positions with animated enter/exit
- hide arrows at first/last slide
- fix vertical centering of phone+description group across all screen sizes
- add smooth blur+slide transition for description text

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

* add contact dropdown with copy email toast

- replace direct mailto link with dropdown: send email or copy email
- install sonner for toast notifications, show top-center on copy
- extract emailAddress constant for clipboard use
- add copy option to mobile hamburger menu too

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

* replace mobile hamburger menu with icon buttons

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

* redesign hero copy, badge-style download buttons, and mobile layout

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

* add consistent padding and object-contain to carousel media

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

* add emote physics background to hero section

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

* move container styling to hero panel, refresh emote set with 2025 trending picks

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

* add staggered entrance animations and remove grid gap

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

* add 30-day cache headers for video and logo assets

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

* add emote collisions and aspect-ratio tracking, refine hero layout

Emote physics: add particle-particle elastic collisions, per-particle
width measurement for correct aspect ratios, new emotes (aga, WW, o7,
FLASHBANG, LULW, Deadass), bump count to 30. Layout: absolute-position
header with z-20, increase mobile carousel ratio to 2fr/4fr, reserve
min-h-10 for description text, remove panel rounding.

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

* fix carousel lint warnings: useSyncExternalStore, ref naming, stable keys

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

* add seo metadata, sitemap, and robots.txt

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

* add privacy link to header and footer credit

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

* update privacy policy content and restyle with mono layout

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

* reorder header nav and add mobile hamburger menu

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

* refresh web dependencies and smooth footer credit hover transition

---------

Co-authored-by: Claude Opus 4.6 <noreply@anthropic.com>

AGENTS.md

@@ -6,21 +6,40 @@
 - When new code supersedes existing functionality, find and remove everything it makes redundant
 - Favor parallel tool calls and subagents when tasks are independent
 
+## Commands
+
+```bash
+flutter pub get                                                     # Install dependencies
+flutter run --dart-define=clientId=ID --dart-define=secret=SECRET   # Run with Twitch credentials
+flutter analyze                                                     # Static analysis (run after changes)
+flutter test                                                        # Run tests (if changes touch testable logic)
+dart run build_runner build                                         # Regenerate .g.dart files (MobX/JSON models)
+dart run build_runner build --delete-conflicting-outputs             # Same, but clears stale outputs
+```
+
+## Source Structure
+
+- `lib/apis/` — API services (all extend `BaseApiClient`)
+- `lib/models/` — Data models (`@JsonSerializable` with `.g.dart` codegen)
+- `lib/screens/{feature}/` — Feature screens with co-located `stores/` subdirectories
+- `lib/stores/` — Global stores only (e.g., `global_assets_store.dart`)
+- `lib/services/` — App-level services
+- `lib/widgets/` — Shared widgets
+- `lib/utils/` — Utility functions
+
 ## Architecture (non-obvious bits)
 
-- Screens live in `lib/screens/{feature}/` with co-located `stores/` subdirectories — don't create top-level store files
+- Feature stores live in `lib/screens/{feature}/stores/` — don't create new top-level store files (only `lib/stores/` holds global stores)
 - All API services extend `BaseApiClient` (`lib/apis/base_api_client.dart`) — don't create standalone API classes
 - MobX stores use a generated mixin pattern — see `lib/screens/settings/stores/auth_store.dart` for the canonical example
 
 ## Gotchas
 
-- Run requires Twitch credentials: `flutter run --dart-define=clientId=YOUR_ID --dart-define=secret=YOUR_SECRET`
-- After changing MobX stores or `@JsonSerializable` models, run `dart run build_runner build`. Never edit `.g.dart` files directly. Use `--delete-conflicting-outputs` if the build fails on stale generated files. Commit `.g.dart` files to source control.
+- After changing MobX stores or `@JsonSerializable` models, regenerate with `dart run build_runner build`. Never edit `.g.dart` files directly. Commit `.g.dart` files to source control.
 - The secure storage cleanup in `main.dart` looks unnecessary but handles an Android/iOS edge case where secure storage persists after uninstall. Don't remove it.
 - Use package imports (`import 'package:frosty/...'`), not relative imports
 - Always include trailing commas
 - Use single quotes
-- Run `flutter analyze` after making changes. Run `flutter test` if changes touch testable logic.
 
 ## Commits