Give plugins access to device-wide config, and a global scroll frame rate

The sports scoreboards read `getattr(self, 'global_config', {})` to find a
shared scroll frame rate, but nothing ever set that attribute: the loader
constructs plugins with only plugin_id/config/display_manager/cache_manager/
plugin_manager (plugin_loader.py:671), `global_config` appears nowhere in
src/, no plugin manager assigns it, and BasePlugin has no __getattr__ to
synthesize it. The lookup always returned {}, so the ten scroll_display.py
copies that thread target_fps through to ScrollHelper could never fire on any
core. There was also no global target_fps to find -- the only one in the
template is display.vegas_scroll.target_fps, which is Vegas-scoped.

Adds the missing half:

- `BasePlugin.global_config` resolves the full config via
  plugin_manager.config_manager, then cache_manager.config_manager, then {}.
  Same order the sports timezone helpers already use. Exceptions are swallowed
  to debug so an unreadable config can never stop a plugin loading, and a
  non-dict result is rejected rather than handed to callers that will .get()
  it and feed the result to numeric code.
- A top-level `target_fps` (default 100), exposed on the General tab and
  validated 30-200 on save to match ScrollHelper.set_target_fps -- which
  clamps silently, so a rejected save reports a value that would otherwise
  appear to save and then behave differently.

The property has a setter deliberately. news, stock-news, ledmatrix-stocks,
ledmatrix-elections, ledmatrix-leaderboard and nfl-draft all assign
`self.global_config = config.get('global', {})`; without a setter that raises
"property has no setter" and those six plugins stop loading. Reproduced, then
pinned with a test.

target_fps is also kept out of the `is_general_update` key list: that branch
treats a missing web_display_autostart as an unchecked box, so counting a
target_fps-only POST as a General save would silently switch autostart off.

Verified end to end: config.json -> BasePlugin.global_config ->
scroll_display's existing block -> ScrollHelper.target_fps 120 -> 100, with no
plugin-side change needed. Suite 1441 passed; the 4 failures
(test_display_dirty_tracking, test_web_api::test_get_system_status, two in
test_state_reconciliation) are pre-existing and reproduce identically on a
clean tree.

Co-Authored-By: Claude Sonnet 5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01KEZK1P1Q1fu5pcuVrkrCFZ

web_interface/templates/v3/partials/general.html

@@ -49,6 +49,18 @@
             <label for="timezone" class="block text-sm font-medium text-gray-700">Timezone{{ ui.help_tip('Time zone used for clocks, schedules, and time-based content.\nChoose the zone where the display physically lives so on/off schedules fire at the correct local time.', 'Timezone') }}</label>
             <div id="timezone_container" class="mt-1"></div>
         </div>
+
+        <!-- Scroll frame rate (device-wide) -->
+        <div class="form-group" id="setting-general-target-fps" data-setting-key="target_fps">
+            <label for="target_fps" class="block text-sm font-medium text-gray-700">Scroll Frame Rate{{ ui.help_tip('Frames per second for scrolling content, applied across plugins that scroll.\nHigher is smoother but uses more CPU; lower frees CPU but looks steppier.\nRange 30-200. Default: 100.', 'Scroll Frame Rate') }}</label>
+            <input type="number"
+                   id="target_fps"
+                   name="target_fps"
+                   value="{{ main_config.target_fps or 100 }}"
+                   min="30"
+                   max="200"
+                   class="form-control">
+        </div>
         <script>
         (function() {
             // Track if already initialized to prevent re-render