refactor: move supporters loading to separate API endpoint

- Add SupportersHandler in misc_handlers.py to serve /api/lm/supporters
- Register new endpoint in misc_route_registrar.py
- Remove supporters from page load template context in model_handlers.py
- Create supportersService.js for frontend data fetching
- Update Header.js to fetch supporters when support modal opens
- Modify support_modal.html to use client-side rendering

This change improves page load performance by loading supporters data
on-demand instead of during initial page render.

py/routes/misc_routes.py

@@ -29,6 +29,7 @@ from .handlers.misc_handlers import (
     NodeRegistry,
     NodeRegistryHandler,
     SettingsHandler,
+    SupportersHandler,
     TrainedWordsHandler,
     UsageStatsHandler,
     build_service_registry_adapter,
@@ -119,6 +120,7 @@ class MiscRoutes:
             metadata_provider_factory=self._metadata_provider_factory,
         )
         custom_words = CustomWordsHandler()
+        supporters = SupportersHandler()
 
         return self._handler_set_factory(
             health=health,
@@ -132,6 +134,7 @@ class MiscRoutes:
             metadata_archive=metadata_archive,
             filesystem=filesystem,
             custom_words=custom_words,
+            supporters=supporters,
         )