feat: add monorepo configuration and shared packages structure

Root-level setup:
- package.json with Turborepo scripts
- pnpm-workspace.yaml for workspace management
- turbo.json for build pipeline
- Common config files (.nvmrc, .prettierrc, .editorconfig)

Shared packages (packages/):
- @manacore/shared-types - Common TypeScript types
- @manacore/shared-supabase - Unified Supabase client
- @manacore/shared-utils - Date, string, async utilities
- @manacore/shared-ui - React Native UI components (placeholder)

🤖 Generated with [Claude Code](https://claude.com/claude-code)

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

turbo.json

@@ -0,0 +1,34 @@
+{
+  "$schema": "https://turbo.build/schema.json",
+  "tasks": {
+    "dev": {
+      "cache": false,
+      "persistent": true
+    },
+    "build": {
+      "dependsOn": ["^build"],
+      "outputs": [
+        "dist/**",
+        "build/**",
+        ".next/**",
+        ".svelte-kit/**",
+        ".astro/**"
+      ]
+    },
+    "lint": {
+      "dependsOn": ["^lint"],
+      "outputs": []
+    },
+    "type-check": {
+      "dependsOn": ["^type-check"],
+      "outputs": []
+    },
+    "test": {
+      "dependsOn": ["^build"],
+      "outputs": ["coverage/**"]
+    },
+    "clean": {
+      "cache": false
+    }
+  }
+}