chore: remove unused imghdr import and dead CSS rules, fix attachment uploader DOM structure, add space after icon spans in templates, and increase test stderr capture limit

tests/conftest.py

@@ -73,7 +73,7 @@ def app_server(test_db_path):
                 proc.wait()
                 raise RuntimeError(
                     f"Server process died (exit code {poll}). "
-                    f"Stderr:\n{stderr[:2000]}"
+                    f"Stderr:\n{stderr[:5000]}"
                 )
             time.sleep(0.5)
     else:
@@ -82,7 +82,7 @@ def app_server(test_db_path):
         proc.wait(timeout=5)
         raise RuntimeError(
             f"Server did not start after 30s. "
-            f"Stderr:\n{stderr[:2000]}"
+            f"Stderr:\n{stderr[:5000]}"
         )
     yield proc
     try: