fix: increase nightly test timeout from 45m to 60m (#2070)

The test suite now takes ~44m30s consistently, leaving no margin.
The April 1 nightly was cancelled after exceeding the 45m limit.

Co-authored-by: Ben Coombs <bjcoombs@users.noreply.github.com>

Author: bjcoombs

.github/workflows/nightly.yml

@@ -90,7 +90,7 @@ jobs:
   slow-integration-tests:
     name: Slow Integration Tests
     runs-on: ubuntu-latest
-    timeout-minutes: 45
+    timeout-minutes: 60
     # Note: No postgres service container needed - tests use testcontainers
     # which manage their own ephemeral containers with proper isolation.