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>

packages/shared-supabase/src/index.ts

@@ -0,0 +1,62 @@
+/**
+ * Shared Supabase utilities for Manacore monorepo
+ *
+ * This package provides a unified Supabase client and common database utilities.
+ */
+
+import { createClient, SupabaseClient } from '@supabase/supabase-js';
+import type { SupabaseConfig } from '@manacore/shared-types';
+
+export { SupabaseClient } from '@supabase/supabase-js';
+
+/**
+ * Create a Supabase client with the given configuration
+ */
+export function createSupabaseClient(config: SupabaseConfig): SupabaseClient {
+  return createClient(config.url, config.anonKey, {
+    auth: {
+      persistSession: true,
+      autoRefreshToken: true,
+    },
+  });
+}
+
+/**
+ * Create a Supabase admin client with service role key
+ */
+export function createSupabaseAdminClient(config: SupabaseConfig): SupabaseClient {
+  if (!config.serviceRoleKey) {
+    throw new Error('Service role key is required for admin client');
+  }
+
+  return createClient(config.url, config.serviceRoleKey, {
+    auth: {
+      persistSession: false,
+      autoRefreshToken: false,
+    },
+  });
+}
+
+/**
+ * Common database query helpers
+ */
+export const dbHelpers = {
+  /**
+   * Handle Supabase query result and return standardized response
+   */
+  handleQueryResult<T>(result: { data: T | null; error: any }): {
+    data: T | null;
+    error: { message: string; code?: string } | null;
+  } {
+    if (result.error) {
+      return {
+        data: null,
+        error: {
+          message: result.error.message,
+          code: result.error.code,
+        },
+      };
+    }
+    return { data: result.data, error: null };
+  },
+};