Fix broken tutorial links to point to existing reference pages

Co-authored-by: xuyushun441-sys <255036401+xuyushun441-sys@users.noreply.github.com>

Author: Copilot

content/docs/tutorials.mdx

@@ -37,7 +37,7 @@ Learn ObjectStack through practical, hands-on tutorials. Each tutorial is design
   />
   <Card
     title="Formula Fields & Calculations"
-    href="./specifications/data/formula"
+    href="./references/data/core/Field"
     description="Build calculated fields and complex business logic"
   />
   <Card
@@ -62,7 +62,7 @@ Learn ObjectStack through practical, hands-on tutorials. Each tutorial is design
   />
   <Card
     title="Create Dashboards"
-    href="./specifications/ui/dashboard"
+    href="./references/ui/analytics/Dashboard"
     description="Build analytics and reporting dashboards"
   />
   <Card
@@ -87,7 +87,7 @@ Learn ObjectStack through practical, hands-on tutorials. Each tutorial is design
   />
   <Card
     title="Permissions & Security"
-    href="./specifications/data/permission"
+    href="./references/data/security/ObjectPermission"
     description="Implement role-based access control"
   />
 </Cards>
@@ -114,8 +114,8 @@ Not sure where to start? Follow this recommended path:
 Complete [Build Your First App](./quick-start/build-first-app) (10 minutes)
 
 ### 2. Choose Your Path
-- **Backend Focus:** [Field Types](./guides/field-types) → [Formulas](./specifications/data/formula) → [Workflows](./guides/workflows-validation)
-- **Frontend Focus:** [Custom Views](./guides/view-configuration) → [Forms](./guides/view-configuration) → [Dashboards](./specifications/ui/dashboard)
+- **Backend Focus:** [Field Types](./guides/field-types) → [Formulas](./references/data/core/Field) → [Workflows](./guides/workflows-validation)
+- **Frontend Focus:** [Custom Views](./guides/view-configuration) → [Forms](./guides/view-configuration) → [Dashboards](./references/ui/analytics/Dashboard)
 - **Full-Stack:** [CRM System](https://github.com/objectstack-ai/spec/tree/main/examples/crm) → [Multi-Tenancy](./guides/advanced/multi-tenancy)
 
 ### 3. Build Your Own