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/package.json

@@ -18,8 +18,10 @@
 		"@sveltejs/vite-plugin-svelte": "^6.2.4",
 		"@tailwindcss/vite": "^4.2.1",
 		"@types/node": "^25.3.3",
+		"clsx": "^2.1.1",
 		"svelte": "^5.51.0",
 		"svelte-check": "^4.4.2",
+		"tailwind-merge": "^3.5.0",
 		"tailwindcss": "^4.2.1",
 		"typescript": "^5.9.3",
 		"vite": "^7.3.1"
@@ -27,7 +29,9 @@
 	"dependencies": {
 		"@aws-sdk/client-s3": "^3.1005.0",
 		"@aws-sdk/s3-request-presigner": "^3.1005.0",
+		"@sentry/sveltekit": "^10.45.0",
 		"cropperjs": "^1.6.2",
+		"ioredis": "^5.3.2",
 		"marked": "^17.0.3",
 		"pocketbase": "^0.26.8"
 	}