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/blueprints/api_v3.py

@@ -747,6 +747,26 @@ def save_main_config():
         if 'timezone' in data:
             current_config['timezone'] = data['timezone']
 
+        # Device-wide scroll frame rate, read by plugins via
+        # BasePlugin.global_config. Bounds match ScrollHelper.set_target_fps,
+        # which clamps silently -- rejecting here instead means a value that
+        # would have been quietly altered is reported rather than appearing to
+        # save and then behaving differently.
+        if 'target_fps' in data and data['target_fps'] not in ('', None):
+            try:
+                target_fps = int(data['target_fps'])
+            except (ValueError, TypeError):
+                return jsonify({
+                    'status': 'error',
+                    'message': "Invalid value for target_fps: must be an integer"
+                }), 400
+            if not (30 <= target_fps <= 200):
+                return jsonify({
+                    'status': 'error',
+                    'message': "Invalid value for target_fps: must be between 30 and 200"
+                }), 400
+            current_config['target_fps'] = target_fps
+
         # Handle location settings
         if 'city' in data or 'state' in data or 'country' in data:
             if 'location' not in current_config:
@@ -1282,7 +1302,7 @@ def save_main_config():
             if key in ['timezone', 'city', 'state', 'country',
                        'web_display_autostart', 'auto_discover',
                        'auto_load_enabled', 'development_mode',
-                       'plugins_directory']:
+                       'plugins_directory', 'target_fps']:
                 continue
             # Skip fields that are already handled above in their own named sections.
             # Without this, every form field name lands as a top-level config key too.