style: clear whitespace, unused-import and blank-line lint

Strip trailing whitespace, drop unused imports/variables/global statements,
split multi-imports, fix E3xx/E1xx spacing and E712 comparisons. No behaviour
change; only E501 long lines remain in flake8.

Co-Authored-By: Claude Sonnet 5.5 <noreply@anthropic.com>

hbd/server/settings.py

@@ -420,7 +420,7 @@ def get_settings_sections(config: dict, threshold_checker=None, user=None) -> li
             "fields": [
                 field("journal_enabled",     "Enabled",          "boolean",
                       "Turn journalling on or off.", editable=True),
-                field("journal_dir",         "Journal directory","path",
+                field("journal_dir",         "Journal directory", "path",
                       "Directory where journal files are written.", editable=True),
                 field("journal_file",        "Journal filename", "text",
                       "Base filename for the journal (rotated copies get a numeric suffix)."),