chore: migrate to pnpm workspaces monorepo with Turborepo

- Restructure directories: apps/api, apps/admin, apps/website
- Add root pnpm-workspace.yaml, turbo.json, .prettierrc, .gitignore
- Rename packages to @inkreach/api, @inkreach/admin, @inkreach/website
- Add shared packages: packages/tsconfig, packages/shared-types
- Add pnpm.onlyBuiltDependencies for native builds
- Update docs: README.md, structs.md
- All three projects build successfully

packages/shared-types/tsconfig.json

@@ -0,0 +1,14 @@
+{
+  "compilerOptions": {
+    "target": "ES2022",
+    "module": "ESNext",
+    "moduleResolution": "bundler",
+    "strict": true,
+    "declaration": true,
+    "declarationMap": true,
+    "outDir": "./dist",
+    "rootDir": "./src",
+    "skipLibCheck": true
+  },
+  "include": ["src"]
+}