chore: migrate to v3, Doppler secrets, clean up legacy code

- Remove all pre-v3 code: scraper, ui-v2, backend v1, ios v1+v2, legacy CI workflows
- Flatten v3/ contents to repo root
- Add Doppler secrets management (project=libnovel, config=prd)
- Add justfile with doppler run wrappers for all docker compose commands
- Strip hardcoded env fallbacks from docker-compose.yml
- Add minimal README.md
- Clean up .gitignore

ui/AGENTS.md

@@ -0,0 +1,71 @@
+# LibNovel UI — Agent Context
+
+SvelteKit 2 + Svelte 5 frontend. Node adapter for production; served behind Caddy.
+
+## Design System
+
+**ACTIVE_STYLE: branded**
+
+Custom amber + zinc dark palette. No shadcn CLI defaults — primitives are hand-authored to match.
+
+| Token | Value |
+|-------|-------|
+| Accent | `#f59e0b` (amber-400) |
+| Surface-1 | zinc-900 |
+| Surface-2 | zinc-800 |
+| Surface-3 | zinc-700 |
+| Text-primary | zinc-100 |
+| Text-secondary | zinc-400 |
+| Destructive | red-400 |
+
+## Tailwind
+
+**Version: 4** — configured entirely via `@theme {}` in `src/app.css` and the `@tailwindcss/vite` plugin.
+
+**There is no `tailwind.config.ts`** — do not create one.
+**Do not run `npx shadcn-svelte add ...`** — primitives are hand-authored in `$lib/components/ui/`.
+
+## shadcn-svelte Primitives
+
+All in `src/lib/components/ui/`:
+
+| Component | Variants / Notes |
+|-----------|-----------------|
+| `button` | default / secondary / outline / ghost / destructive / link; sizes: default / sm / lg / icon |
+| `badge` | default / secondary / outline / destructive |
+| `card` | Card, CardHeader, CardTitle, CardDescription, CardContent, CardFooter |
+| `textarea` | bindable `value` prop |
+| `dialog` | Dialog, DialogContent, DialogHeader, DialogTitle, DialogFooter |
+| `separator` | horizontal / vertical |
+
+Always use `cn()` from `$lib/utils` — never template-literal class conditionals.
+
+## Svelte 5 Conventions
+
+- `@Observable` / runes (`$state`, `$derived`, `$effect`, `$props()`) for all new code.
+- Do not add `ObservableObject` / `@Published` — they don't exist in Svelte; don't introduce legacy `writable` stores for new code.
+- Navigation: `goto()` from `$app/navigation`; `page` from `$app/state`.
+
+## iOS/UX Skill
+
+For any view work, load the `ios-ux` skill at task start:
+```
+skill({ name: "ios-ux" })
+```
+
+## Key Files
+
+| File | Role |
+|------|------|
+| `src/app.css` | Tailwind v4 `@theme` tokens — source of truth for all design tokens |
+| `src/lib/utils.ts` | `cn()` helper (clsx + tailwind-merge) |
+| `src/lib/types.ts` | Shared client-safe domain types |
+| `src/routes/+layout.svelte` | Root layout: sticky nav, persistent `<audio>` element, mini-player bar |
+| `src/lib/audio.svelte.ts` | Global audio store (Svelte 5 runes class) |
+| `src/lib/components/ui/` | shadcn-style UI primitives |
+
+## Persistent Audio Element
+
+The `<audio>` element in `+layout.svelte` **must never be conditionally rendered** (no `{#if}`).
+Conditional rendering destroys and recreates the element, triggering `onpause` mid-playback.
+Keep it always in the DOM; control it via `audioStore`.