feat: retro blog engine with swappable OS/console themes

Next.js 16 (App Router, TS) + SQLite (better-sqlite3) + marked.

Core: a shared semantic HTML skeleton (rb- classes in Shell.tsx) that
each theme reskins via a scoped [data-theme="..."] CSS file. Theme is
persisted in a cookie, resolved server-side in the root layout, and
swapped live by the client switcher (no reload, no FOUC).

- DB auto-migrates and seeds posts on first run (data/blog.db, gitignored)
- Pages: post list, post detail (markdown), about
- Themes shipped: Windows XP (Luna), Windows 9x, PlayStation 2
- Adding a skin = registry entry + one scoped CSS file

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

tsconfig.json

@@ -0,0 +1,34 @@
+{
+  "compilerOptions": {
+    "target": "ES2017",
+    "lib": ["dom", "dom.iterable", "esnext"],
+    "allowJs": true,
+    "skipLibCheck": true,
+    "strict": true,
+    "noEmit": true,
+    "esModuleInterop": true,
+    "module": "esnext",
+    "moduleResolution": "bundler",
+    "resolveJsonModule": true,
+    "isolatedModules": true,
+    "jsx": "react-jsx",
+    "incremental": true,
+    "plugins": [
+      {
+        "name": "next"
+      }
+    ],
+    "paths": {
+      "@/*": ["./src/*"]
+    }
+  },
+  "include": [
+    "next-env.d.ts",
+    "**/*.ts",
+    "**/*.tsx",
+    ".next/types/**/*.ts",
+    ".next/dev/types/**/*.ts",
+    "**/*.mts"
+  ],
+  "exclude": ["node_modules"]
+}