fix(core): font zip cache, monotonic timers, resolver back-off, and other core/common fixes (#654)

* fix(core): font zip cache, monotonic timers, resolver back-off, and other core/common fixes

- font_manager: a .zip font URL is served as its extracted font after a
  restart (the cached-file check returned the archive first); downloads
  use requests with a 30s timeout into a temp file + os.replace.
- api_helper / sync_manager: rate-limit and heartbeat/leader timeouts use
  time.monotonic(); last_request_time and the status file's ts stay
  wall-clock. set_on_new_cycle docstring no longer claims core uses it.
- logo_helper: the placeholder uses the same scaled box as a real logo.
- permission_utils: one _sudo_bash_candidates() helper (with the sudoers
  exact-argv rationale) shared by sudo_remove_directory, which now retries
  the next bash path on a sudo refusal, and install_requirements_file.
- dynamic_team_resolver: failed/empty fetch backs off 5 min; duplicate
  INFO log and contradictory docstring example fixed.
- element_style: scale default looked up through element aliases.
- background_data_service: cache-hit callback runs outside the lock.
- config_arrays: union-aware type check (["array","null"]); stale
  dotToNested() reference removed.
- auto_update_setup: non-dict auto_update reads as off; temp result file
  unlinked when the write fails.
- exceptions: constructors copy the caller's context dict.
- logging_config: StructuredFormatter json.dumps(default=str).
- error_aggregator: removed unused export_path/export_to_file/_auto_export.
- Docstrings: validate_file_upload max_size_mb, raise_on_errors.

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

* fix(sync): retry the status-file rename like the other atomic writers

On Windows os.replace can fail with "Access is denied" while a scanner
briefly holds the target open; config_manager_atomic._replace already
retries that (and re-raises at once on other platforms). The sync status
writer called os.replace directly, which made
test_concurrent_writers_each_use_their_own_temp_file flaky on Windows.

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

---------

Co-authored-by: Claude Opus 5.5 <noreply@anthropic.com>

test/web_interface/test_config_arrays.py

@@ -30,6 +30,22 @@ def test_element_types_are_left_to_normalization():
     assert config["color"] == ["1", "2", "3"]
 
 
+def test_a_nullable_array_union_is_still_an_array():
+    """["array", "null"] is how the per-mode style overrides are typed (null
+    means inherit); their indexed colour inputs must still recombine."""
+    config = {"text_color": {"0": 1, "1": 2, "2": 3}}
+    coerce_array_shapes(config, {"text_color": {"type": ["array", "null"]}})
+    assert config["text_color"] == [1, 2, 3]
+
+
+def test_a_nullable_object_union_is_walked_into():
+    config = {"live": {"tags": {"0": "a"}}}
+    coerce_array_shapes(config, {"live": {
+        "type": ["object", "null"],
+        "properties": {"tags": {"type": "array"}}}})
+    assert config["live"]["tags"] == ["a"]
+
+
 def test_nested_objects_and_array_items_are_walked():
     schema = {"feeds": {"type": "object", "properties": {
         "custom_feeds": {"type": "array", "items": {"type": "object", "properties": {