fix: include db/migrations in publish package

Problem: Migrations were copied to ./publish/migrations but app looks for db/migrations
Solution: Copy to ./publish/db/migrations to match working directory structure

This ensures V020, V021, V022 migrations run automatically on app startup.

.gitea/workflows/deploy.yml

@@ -75,7 +75,7 @@ jobs:
           test -s ./publish/proxy/TaxBaik.Proxy.runtimeconfig.json || { echo "TaxBaik.Proxy.runtimeconfig.json missing" >&2; exit 1; }
 
       - name: Copy migrations
-        run: cp -r db/migrations ./publish/migrations || true
+        run: mkdir -p ./publish/db && cp -r db/migrations ./publish/db/ || true
 
       - name: Generate build info
         run: |