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>

src/common/sync_manager.py

@@ -32,6 +32,7 @@ from typing import Callable, Optional
 import numpy as np
 from PIL import Image
 
+from src.config_manager_atomic import _replace
 from src.display_geometry import DEFAULT_CHAIN_LENGTH, DEFAULT_COLS, DEFAULT_ROWS
 
 # Raw-frame wire format: 8-byte magic + 4-byte header + raw RGB pixels
@@ -127,6 +128,9 @@ class DisplaySyncManager:
         self._peer_ip: Optional[str] = None
         self._peer_compatible: bool = False
         self._peer_chain: int = 0
+        # time.monotonic() readings, like _last_leader_frame_time: these only
+        # feed the timeout watchdogs, and a wall-clock step (NTP correcting a
+        # Pi with no RTC) would otherwise fake or mask a timeout.
         self._last_heartbeat_time: float = 0.0
         self._leader_width: int = 0  # set by display_controller after init
         self._oversized_frame_warned: bool = False
@@ -206,7 +210,7 @@ class DisplaySyncManager:
                     self._handle_hello(msg, sender_ip)
                 elif t == "hb":
                     if self._peer_ip == sender_ip:
-                        self._last_heartbeat_time = time.time()
+                        self._last_heartbeat_time = time.monotonic()
             except socket.timeout:
                 continue
             except Exception as exc:
@@ -229,7 +233,7 @@ class DisplaySyncManager:
         self._peer_ip = sender_ip
         self._peer_compatible = compatible
         self._peer_chain = peer_chain
-        self._last_heartbeat_time = time.time()
+        self._last_heartbeat_time = time.monotonic()
 
         prev_state = self._leader_state
         if compatible:
@@ -273,7 +277,7 @@ class DisplaySyncManager:
         while self._running:
             time.sleep(1.0)
             if self._leader_state == LeaderState.CONNECTED:
-                if time.time() - self._last_heartbeat_time > PEER_TIMEOUT:
+                if time.monotonic() - self._last_heartbeat_time > PEER_TIMEOUT:
                     self.logger.info(
                         "Sync: follower heartbeat timeout — peer disconnected"
                     )
@@ -501,7 +505,7 @@ class DisplaySyncManager:
         """Note that the leader at ``sender_ip`` just sent something, and
         switch from standalone to follower mode if not already following.
         Returns True if this call made the switch."""
-        self._last_leader_frame_time = time.time()
+        self._last_leader_frame_time = time.monotonic()
         self._leader_ip = sender_ip
         if self._follower_state != FollowerState.STANDALONE:
             return False
@@ -621,11 +625,13 @@ class DisplaySyncManager:
         heartbeat = json.dumps({"t": "hb"}).encode("utf-8")
         dest = ("<broadcast>", self.port)
 
-        last_hello = 0.0
-        last_hb = 0.0
+        # -inf, not 0.0: monotonic time starts near boot, so "now - 0.0" can
+        # be under the interval and would delay the first announcement.
+        last_hello = float("-inf")
+        last_hb = float("-inf")
 
         while self._running:
-            now = time.time()
+            now = time.monotonic()
             if now - last_hello >= HELLO_INTERVAL:
                 try:
                     self._send_sock.sendto(hello, dest)
@@ -644,7 +650,7 @@ class DisplaySyncManager:
         while self._running:
             time.sleep(1.0)
             if self._follower_state == FollowerState.FOLLOWER:
-                if time.time() - self._last_leader_frame_time > LEADER_TIMEOUT:
+                if time.monotonic() - self._last_leader_frame_time > LEADER_TIMEOUT:
                     self.logger.info(
                         "Sync: leader frame timeout — returning to standalone mode"
                     )
@@ -670,7 +676,10 @@ class DisplaySyncManager:
 
     def set_on_new_cycle(self, callback: Callable[[], None]) -> None:
         """Follower: register a callback fired when the leader starts a new scroll cycle.
-        Used to trigger a local start_new_cycle() so both Pis rebuild from same fresh data.
+
+        Nothing in core registers one: display_controller follows the leader
+        through set_on_scroll_image() and the scroll position instead of
+        rebuilding locally. The hook stays for callers that want the signal.
         """
         self._on_new_cycle = callback
 
@@ -734,7 +743,9 @@ class DisplaySyncManager:
                 # mkstemp makes it owner-only; the web UI may run as a
                 # different user from the display service.
                 os.chmod(tmp, 0o644)
-                os.replace(tmp, STATUS_FILE)
+                # _replace: on Windows a rename can briefly fail with
+                # "Access is denied" while a scanner holds the target open.
+                _replace(tmp, STATUS_FILE)
                 tmp = None
         except Exception as exc:
             self.logger.debug("Sync: status file write error: %s", exc)