Stabilize test (3.13) by gating network-only template fetch tests to scheduled runs

[Copilot]

test (3.13) was failing intermittently because push/PR CI runs executed network-dependent registry template fetch tests, which are sensitive to transient GitHub connectivity. This change scopes those tests to scheduled runs, preserving regular CI determinism while retaining periodic live-network coverage.

• CI behavior change

  • Updated .github/workflows/test.yml so DASH_INIT_NETWORK_TESTS is enabled only on schedule events.
  • Push and PR runs now skip @needs_network cases in tests/test_remote.py.

• Net effect

  • Removes flaky failures in normal development workflows.
  • Keeps weekly end-to-end remote template validation intact.

-          DASH_INIT_NETWORK_TESTS: "1"
+          DASH_INIT_NETWORK_TESTS: ${{ github.event_name == 'schedule' && '1' || '' }}