chore: add migration check job to CI workflow + fix missaligned db migration (#3476)

## Summary

- Adds a new `migration-check` CI job that runs `./gradlew
diffChangeLog` and fails if migration files are out of date
- Reuses the backend build artifact (same as `schema-check` and
`backend-test`)
- Wired into `everything-passed` gate so PRs with stale migrations
cannot merge

<!-- This is an auto-generated comment: release notes by coderabbit.ai
-->
## Summary by CodeRabbit

* **Chores**
* CI pipeline now includes an automated migration check that validates
database migration files are up-to-date before completing builds.

* **Refactor**
* Database indexing was adjusted to change how certain activity records
are indexed, improving query behavior and performance in relevant
lookups.
<!-- end of auto-generated comment: release notes by coderabbit.ai -->

---------

Co-authored-by: Daniel Krizan <danyelkrizan@gmail.com>

Author: Anty0

.github/workflows/test.yml

@@ -322,6 +322,40 @@ jobs:
           fi
           echo "✅ Schema files are up to date"
 
+  migration-check:
+    name: Migration Check 🗃️
+    needs: [backend-build]
+    runs-on: ubuntu-24.04
+    steps:
+      - uses: actions/checkout@v4
+
+      - name: Setup environment
+        uses: ./.github/actions/setup-env
+        with:
+          node: "false"
+
+      - name: Download backend build result
+        uses: ./.github/actions/download-backend-build
+
+      - name: Generate migration diff
+        run: ./gradlew diffChangeLog
+        env:
+          SKIP_SERVER_BUILD: true
+
+      - name: Check for uncommitted migration changes
+        run: |
+          if [ -n "$(git status --porcelain)" ]; then
+            echo "❌ Migration files are out of date! Please run './gradlew diffChangeLog' locally and commit the changes."
+            echo ""
+            echo "Changed files:"
+            git status --porcelain
+            echo ""
+            echo "Diff:"
+            git diff
+            exit 1
+          fi
+          echo "✅ Migration files are up to date"
+
   e2e-code-checks:
     name: E2E Static Check 🪲
     runs-on: ubuntu-24.04
@@ -399,6 +433,7 @@ jobs:
       - frontend-build
       - frontend-code-check
       - schema-check
+      - migration-check
       - e2e
       - e2e-code-checks
       - e2e-install-deps
@@ -433,6 +468,10 @@ jobs:
             failed_jobs+=("schema-check")
           fi
 
+          if [[ "${{ needs.migration-check.result }}" != "success" ]]; then
+            failed_jobs+=("migration-check")
+          fi
+
           if [[ "${{ needs.e2e.result }}" != "success" ]]; then
             failed_jobs+=("e2e")
           fi

backend/data/src/main/kotlin/io/tolgee/model/activity/ActivityModifiedEntity.kt

@@ -21,7 +21,7 @@ import java.io.Serializable
 @Entity
 @Table(
   indexes = [
-    Index(columnList = "branch_id"),
+    Index(columnList = "activity_revision_id,branch_id"),
   ],
 )
 @IdClass(ActivityModifiedEntityId::class)