refactor: rebuild template — Tailwind v4, Docker self-hosting, passkey auth

Toolchain fixes (all previously broken):
- npm run lint: next lint was removed in Next 16 -> eslint with flat config
- .eslintrc.json was ignored by ESLint 9 -> eslint.config.mjs
- npm test / test:e2e exited 1 with no tests -> passWithNoTests
- Vitest scanned tests/ and would have run Playwright specs -> scoped to src/
- Playwright targeted Mobile Safari while docs installed only chromium
- reuseExistingServer silently tested a foreign server on :3000 -> E2E_PORT
- 11 high-severity vulns -> npm audit fix
- deny rule Read(**/.env*) also blocked .env.example -> precise patterns

Stack changes:
- Tailwind v3 -> v4 (CSS-first, no tailwind.config.ts, tw-animate-css)
- shadcn regenerated for v4; 33 components -> 6 core, bundled radix-ui
- Supabase removed entirely; data layer is now chosen per project
- Vercel removed; Docker Compose self-hosting with scripts/update.sh
- Better Auth + passkey plugin as the binding auth standard
- ThemeProvider and Sonner mounted; dark mode and toasts now actually work

Workflow system:
- Sub-agents wired: /frontend, /backend, /qa delegate to .claude/agents
- Checklists folded into their SKILL.md; one file per skill
- Rules rewritten: DB-agnostic backend, passkey security, v4 frontend
- Spec language settled as German, skill instructions English

package.json

@@ -1,53 +1,35 @@
 {
   "name": "ai-coding-starter-kit",
   "version": "1.0.0",
-  "description": "AI Coding Starter Kit with AI Agent Team System for Claude Code",
+  "description": "Next.js starter with an AI-driven development workflow (skills, agents, feature specs) for Claude Code",
   "private": true,
   "scripts": {
     "dev": "next dev",
     "build": "next build",
     "start": "next start",
-    "lint": "next lint",
-    "test": "vitest run",
+    "lint": "eslint .",
+    "typecheck": "tsc --noEmit",
+    "test": "vitest run --passWithNoTests",
     "test:watch": "vitest",
-    "test:e2e": "playwright test",
-    "test:e2e:ui": "playwright test --ui",
-    "test:all": "vitest run && playwright test"
+    "test:e2e": "playwright test --pass-with-no-tests",
+    "test:all": "npm run test && npm run test:e2e",
+    "docker:up": "docker compose up -d --build",
+    "docker:down": "docker compose down",
+    "docker:logs": "docker compose logs -f app"
   },
   "dependencies": {
     "@hookform/resolvers": "^5.2.2",
-    "@radix-ui/react-accordion": "^1.2.12",
-    "@radix-ui/react-alert-dialog": "^1.1.15",
-    "@radix-ui/react-avatar": "^1.1.11",
-    "@radix-ui/react-checkbox": "^1.3.3",
-    "@radix-ui/react-collapsible": "^1.1.12",
-    "@radix-ui/react-dialog": "^1.1.15",
-    "@radix-ui/react-dropdown-menu": "^2.1.16",
-    "@radix-ui/react-label": "^2.1.8",
-    "@radix-ui/react-navigation-menu": "^1.2.14",
-    "@radix-ui/react-popover": "^1.1.15",
-    "@radix-ui/react-progress": "^1.1.8",
-    "@radix-ui/react-radio-group": "^1.3.8",
-    "@radix-ui/react-scroll-area": "^1.2.10",
-    "@radix-ui/react-select": "^2.2.6",
-    "@radix-ui/react-separator": "^1.1.8",
-    "@radix-ui/react-slot": "^1.2.4",
-    "@radix-ui/react-switch": "^1.2.6",
-    "@radix-ui/react-tabs": "^1.1.13",
-    "@radix-ui/react-toast": "^1.2.15",
-    "@radix-ui/react-tooltip": "^1.2.8",
-    "@supabase/supabase-js": "^2.39.3",
     "class-variance-authority": "^0.7.1",
     "clsx": "^2.1.0",
-    "cmdk": "^1.1.1",
     "lucide-react": "^0.562.0",
     "next": "^16.1.1",
     "next-themes": "^0.4.6",
+    "radix-ui": "^1.6.7",
     "react": "^19.0.0",
     "react-dom": "^19.0.0",
     "react-hook-form": "^7.71.1",
     "sonner": "^2.0.7",
-    "tailwind-merge": "^2.2.0",
+    "tailwind-merge": "^3.6.0",
     "zod": "^4.3.5"
   },
   "devDependencies": {