fix(astrolabe): Fix NcSelect options and CSS loading

- Use :input-label prop for NcSelect field labels instead of :label
  (the :label prop sets the option label property key, not the visible label)
- Fix CSS loading in admin.php and personal.php templates to use
  astrolabe-main (the bundled CSS file)
- Update minimum Nextcloud version to 31 (required for Vue 3)

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

third_party/astrolabe/src/components/admin/AdminSettings.vue

@@ -154,7 +154,7 @@
 					<NcSelect
 						:model-value="selectedAlgorithmOption"
 						:options="algorithmOptions"
-						:label="t('astrolabe', 'Search Algorithm')"
+						:input-label="t('astrolabe', 'Search Algorithm')"
 						class="form-field"
 						@update:model-value="settings.algorithm = $event ? $event.id : 'hybrid'" />
 					<p class="help-text">
@@ -164,7 +164,7 @@
 					<NcSelect
 						:model-value="selectedFusionOption"
 						:options="fusionOptions"
-						:label="t('astrolabe', 'Fusion Method')"
+						:input-label="t('astrolabe', 'Fusion Method')"
 						class="form-field"
 						@update:model-value="settings.fusion = $event ? $event.id : 'rrf'" />
 					<p class="help-text">