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>

.prettierrc

@@ -0,0 +1,26 @@
+{
+  "semi": true,
+  "trailingComma": "es5",
+  "singleQuote": true,
+  "printWidth": 100,
+  "tabWidth": 2,
+  "useTabs": false,
+  "bracketSpacing": true,
+  "arrowParens": "always",
+  "endOfLine": "lf",
+  "plugins": ["prettier-plugin-svelte", "prettier-plugin-astro"],
+  "overrides": [
+    {
+      "files": "*.svelte",
+      "options": {
+        "parser": "svelte"
+      }
+    },
+    {
+      "files": "*.astro",
+      "options": {
+        "parser": "astro"
+      }
+    }
+  ]
+}