feat(activeDid): implement migration to separate active_identity table

- Add migration 003 with data migration logic to prevent data loss
- Create dedicated ActiveIdentity interface in separate file for better architecture
- Implement $getActiveIdentity method in PlatformServiceMixin
- Enhance $updateActiveDid with dual-write pattern for backward compatibility
- Maintain separation of concerns between settings and active identity types
- Follow project architectural pattern with dedicated type definition files

The migration creates active_identity table alongside existing settings,
automatically copying existing activeDid data to prevent user data loss.
Dual-write pattern ensures backward compatibility during transition.

Migration includes:
- Schema creation with proper constraints and indexes
- Automatic data transfer from settings.activeDid to active_identity.activeDid
- Validation to ensure data exists before migration
- Atomic operation: schema and data migration happen together

src/utils/PlatformServiceMixin.ts

@@ -58,6 +58,7 @@ import {
   generateInsertStatement,
   generateUpdateStatement,
 } from "@/utils/sqlHelpers";
+import { ActiveIdentity } from "@/db/tables/activeIdentity";
 
 // =================================================
 // TYPESCRIPT INTERFACES
@@ -548,6 +549,40 @@ export const PlatformServiceMixin = {
       }
     },
 
+    /**
+     * Get active identity from the new active_identity table
+     * This replaces the activeDid field in settings for better architecture
+     */
+    async $getActiveIdentity(): Promise<ActiveIdentity> {
+      try {
+        const result = await this.$dbQuery(
+          "SELECT id, activeDid, lastUpdated FROM active_identity WHERE id = 1",
+        );
+
+        if (result?.values?.length) {
+          const [id, activeDid, lastUpdated] = result.values[0];
+          return {
+            id: id as number,
+            activeDid: activeDid as string,
+            lastUpdated: lastUpdated as string,
+          };
+        }
+
+        // Return default if no record exists
+        return {
+          id: 1,
+          activeDid: "",
+          lastUpdated: new Date().toISOString(),
+        };
+      } catch (error) {
+        logger.error(
+          "[PlatformServiceMixin] Error getting active identity:",
+          error,
+        );
+        throw error;
+      }
+    },
+
     /**
      * Transaction wrapper with automatic rollback on error
      */