Defer server file changes until guarded restart activation

Persist beta, promotion, drift, and rollback payloads until occupancy and restart-capacity checks pass. Preserve rollback snapshots and campaign ordering, and allow held rollback campaigns to resume safely.

Fixes #28

Validation: 805 tests passed, Svelte checks clean, production build passed.

src/routes/api/campaigns/[id]/+server.ts

@@ -17,7 +17,8 @@ export async function GET({ params }: { params: { id: string } }) {
         .prepare(
             `SELECT id, server, verb, rel_path, sha256_before, sha256_after,
                     LENGTH(content_before) AS size_before,
-                    LENGTH(content_after)  AS size_after
+                    LENGTH(content_after)  AS size_after,
+                    COALESCE((SELECT state FROM staged_file_changes WHERE deployment_file_id = deployment_files.id), 'applied') AS apply_state
              FROM deployment_files
              WHERE deployment_id = ?
              ORDER BY server, rel_path`