fix: web UI and src.common bugs (wifi wrong-password, plugin icon, starlark toggle, API caching, scroll/logo/font helpers) (#646)

- wifi: keep the "wrong_password:" prefix through the restore/AP fallback so
  the UI's incorrect-password prompt fires again.
- /plugins/installed returns the manifest's icon (string only).
- /starlark/apps/<id>/toggle coerces `enabled` and delegates to
  _toggle_starlark_app (disk before memory, no KeyError, "false" is false).
- /api/v3/ JSON GETs are sent Cache-Control: no-store; non-JSON keeps 5s.
- ScrollHelper.set_scrolling_image converts non-RGB input (alpha onto black);
  create/set_scrolling_image reset last_update_time like reset_scroll.
- LogoHelper backs off a failed download per path for
  MISSING_LOGO_RECHECK_SECONDS; cleared on invalidate/clear_cache.
- refresh_placeholder_timestamp saves atomically.
- FontManager.clear_cache / _clear_plugin_font_cache bump cache_generation.
- Odds manager: per-game logs to DEBUG; JSON decode error caught before
  RequestException (same cooldown).
- element_style mangled continuations; startup validator skips null plugin
  blocks and reuses the controller's discovery.
- src/common/README lists frame_timing, json_body, render_gate.

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

test/test_wifi_wrong_password_signal.py

@@ -0,0 +1,78 @@
+"""A rejected passphrase must reach the web UI as "wrong_password:".
+
+_connect_nmcli prefixes the message with "wrong_password:" and the api_v3
+wifi route turns that into ``error_type == 'wrong_password'``, which the
+setup pages key their "incorrect password" prompt off. _connect_validated
+used to replace the message on every failure branch (restore the old
+network, or bring the setup AP up), so the prefix never survived.
+"""
+
+import sys
+from pathlib import Path
+from types import SimpleNamespace
+from unittest.mock import MagicMock, patch
+
+import pytest
+
+sys.path.insert(0, str(Path(__file__).parent.parent))
+
+from src.wifi_manager import WiFiManager  # noqa: E402
+
+
+def _manager(connected_ssid=None):
+    manager = WiFiManager.__new__(WiFiManager)  # no __init__: no real host access
+    manager.has_nmcli = True
+    manager._wifi_interface = "wlan0"
+    manager.get_wifi_status = MagicMock(return_value=SimpleNamespace(
+        connected=bool(connected_ssid), ssid=connected_ssid, ip_address=None))
+    manager._is_ap_mode_active = MagicMock(return_value=False)
+    manager._ensure_wifi_radio_enabled = MagicMock(return_value=True)
+    manager._show_led_message = MagicMock()
+    manager.disconnect_from_network = MagicMock(return_value=(True, "ok"))
+    manager._wait_for_device_idle = MagicMock(return_value=True)
+    manager.enable_ap_mode = MagicMock(return_value=(True, "AP up"))
+    return manager
+
+
+def _run(manager, nmcli_result):
+    manager._connect_nmcli = MagicMock(return_value=nmcli_result)
+    nmcli_out = SimpleNamespace(returncode=0, stdout="GENERAL.CONNECTION:OldNet\n")
+    with patch("src.wifi_manager.subprocess.run", return_value=nmcli_out), \
+            patch("src.wifi_manager.time.sleep"):
+        return manager._connect_validated("HomeNet", "hunter22")
+
+
+WRONG = (False, "wrong_password: Secrets were required, but not provided")
+
+
+class TestWrongPasswordSurvivesRecovery:
+    def test_when_the_setup_ap_comes_back_up(self):
+        ok, message = _run(_manager(), WRONG)
+        assert ok is False
+        assert message.startswith("wrong_password:")
+
+    def test_when_the_setup_ap_fails_too(self):
+        manager = _manager()
+        manager.enable_ap_mode.return_value = (False, "hostapd missing")
+        ok, message = _run(manager, WRONG)
+        assert ok is False
+        assert message.startswith("wrong_password:")
+        assert "hostapd missing" in message
+
+    @pytest.mark.parametrize("restored", [True, False])
+    def test_when_the_previous_network_is_restored_or_not(self, restored):
+        manager = _manager(connected_ssid="OldNet")
+        manager._restore_original_connection = MagicMock(return_value=restored)
+        ok, message = _run(manager, WRONG)
+        assert ok is False
+        assert message.startswith("wrong_password:")
+
+
+class TestOtherFailuresAreUnchanged:
+    def test_a_generic_failure_gets_no_prefix(self):
+        ok, message = _run(_manager(), (False, "Connection timed out"))
+        assert ok is False
+        assert message == "Connection failed. AP mode enabled."
+
+    def test_success_passes_through(self):
+        assert _run(_manager(), (True, "Connected to HomeNet")) == (True, "Connected to HomeNet")