Feat/pipeline specified plugins (#1752)

* feat: add persistence field

* feat: add basic extension page in pipeline config

* Merge pull request #1751 from langbot-app/copilot/add-plugin-extension-tab

Implement pipeline-scoped plugin binding system

* fix: i18n keys

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Co-authored-by: Copilot <198982749+Copilot@users.noreply.github.com>

web/src/i18n/locales/en-US.ts

@@ -427,6 +427,17 @@ const enUS = {
     defaultPipelineCannotDelete: 'Default pipeline cannot be deleted',
     deleteSuccess: 'Deleted successfully',
     deleteError: 'Delete failed: ',
+    extensions: {
+      title: 'Plugins',
+      loadError: 'Failed to load plugins',
+      saveSuccess: 'Saved successfully',
+      saveError: 'Save failed',
+      noPluginsAvailable: 'No plugins available',
+      disabled: 'Disabled',
+      noPluginsSelected: 'No plugins selected',
+      addPlugin: 'Add Plugin',
+      selectPlugins: 'Select Plugins',
+    },
     debugDialog: {
       title: 'Pipeline Chat',
       selectPipeline: 'Select Pipeline',