refactor: implement team feedback for active identity migration structure

- Update migration 003 to match master deployment (hasBackedUpSeed)
- Rename migration 004 for active_identity table creation
- Update migration service validation for new structure
- Fix TypeScript compatibility issue in migration.ts
- Streamline active identity upgrade plan documentation
- Ensure all migrations are additional per team guidance

Migration structure now follows "additional migrations only" principle:
- 003: hasBackedUpSeed (assumes master deployment)
- 004: active_identity table with data migration
- iOS/Android compatibility confirmed with SQLCipher 4.9.0

Files: migration.ts, migrationService.ts, active-identity-upgrade-plan.md

src/db-sql/migration.ts

@@ -35,7 +35,7 @@ interface DatabaseResult {
 // where they couldn't take action because they couldn't unlock that identity.)
 
 const randomBytes = crypto.getRandomValues(new Uint8Array(32));
-const secretBase64 = arrayBufferToBase64(randomBytes);
+const secretBase64 = arrayBufferToBase64(randomBytes.buffer);
 
 // Each migration can include multiple SQL statements (with semicolons)
 const MIGRATIONS = [
@@ -132,8 +132,20 @@ const MIGRATIONS = [
     `,
   },
   {
-    name: "003_active_identity_and_seed_backup",
+    name: "003_add_hasBackedUpSeed_to_settings",
     sql: `
+      -- Add hasBackedUpSeed field to settings
+      -- This migration assumes master code has been deployed
+      -- The error handling will catch this if column already exists and mark migration as applied
+      ALTER TABLE settings ADD COLUMN hasBackedUpSeed BOOLEAN DEFAULT FALSE;
+    `,
+  },
+  {
+    name: "004_active_identity_and_seed_backup",
+    sql: `
+      -- Migration 004: active_identity_and_seed_backup
+      -- Assumes master code deployed with migration 003 (hasBackedUpSeed)
+      
       -- Enable foreign key constraints for data integrity
       PRAGMA foreign_keys = ON;
       
@@ -152,7 +164,6 @@ const MIGRATIONS = [
       CREATE UNIQUE INDEX IF NOT EXISTS idx_active_identity_single_record ON active_identity(id);
 
       -- Seed singleton row (only if not already exists)
-      -- Use a more explicit approach to ensure the row gets inserted
       INSERT INTO active_identity (id, activeDid, lastUpdated) 
       SELECT 1, NULL, datetime('now') 
       WHERE NOT EXISTS (SELECT 1 FROM active_identity WHERE id = 1);
@@ -174,15 +185,6 @@ const MIGRATIONS = [
       SELECT 'DEBUG: Row count after insertion' as debug_message, COUNT(*) as row_count FROM active_identity;
     `,
   },
-  {
-    name: "003b_add_hasBackedUpSeed_to_settings",
-    sql: `
-      -- Add hasBackedUpSeed field to settings
-      -- This may fail if column already exists from master branch migration
-      -- The error handling will catch this and mark migration as applied
-      ALTER TABLE settings ADD COLUMN hasBackedUpSeed BOOLEAN DEFAULT FALSE;
-    `,
-  },
 ];
 
 /**