💚(ci) improve E2E tests

Disable retries and save trace for failed tests.

💚(ci) preserve server logs

Save server logs to the same place as Playwright reports to aid debugging.

💚(ci) move back to 1 worker on CI

At least three reasons
- seems redundant with sharding
- strong suspicion it's the reason for the ValidationError issue
- that way the comment no longer tells a lie ;)

💚(ci) improve E2E tests

Log into CHANGELOG to ensure the new test results impact PR status 🤷

💚(ci) make dummy data creation more robust

This is a QR (Quick Response) fix for the failures in the "Add dummy
data" step in E2E testing. Proper QC (Quality Control) needs a bit
more thought.

src/backend/demo/management/commands/create_demo.py

@@ -156,8 +156,13 @@ def create_demo(stdout):
         queue.flush()
 
     with Timeit(stdout, "Creating domains"):
+        created = set()
         for _i in range(defaults.NB_OBJECTS["domains"]):
             name = fake.domain_name()
+            if name in created:
+                continue
+            created.add(name)
+
             slug = slugify(name)
 
             queue.push(