feat(dispatch): implement dispatch-workflow.sh with dispatch, poll, and timeout

Add dispatch-workflow.sh script that dispatches a Gitea workflow
in another repository and polls synchronously for completion.
Refactor mock-api.sh to use Python3 HTTP server with sequence
support, enabling stateful poll-response simulation in tests.

docs/tickets/0002-dispatch-workflow-sh.md

@@ -1,7 +1,7 @@
 # Ticket 0002: `dispatch-workflow.sh`
 
 **Vaihe:** 2/12
-**Status:** pending
+**Status:** done
 **Feature branch:** `feature/0002-dispatch-workflow-sh`
 **TDD required:** Yes
 **Feature file required:** Yes