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/tsconfig/api.json

@@ -0,0 +1,20 @@
+{
+  "$schema": "https://json.schemastore.org/tsconfig",
+  "extends": "./base.json",
+  "compilerOptions": {
+    "module": "commonjs",
+    "target": "ES2021",
+    "emitDecoratorMetadata": true,
+    "experimentalDecorators": true,
+    "removeComments": true,
+    "strictNullChecks": true,
+    "noImplicitAny": true,
+    "strictBindCallApply": true,
+    "outDir": "./dist",
+    "baseUrl": "./",
+    "incremental": true,
+    "paths": {
+      "@/*": ["src/*"]
+    }
+  }
+}