Semantic Search Triggers (#18969)

* semantic trigger test

* database and model

* config

* embeddings maintainer and trigger post-processor

* api to create, edit, delete triggers

* frontend and i18n keys

* use thumbnail and description for trigger types

* image picker tweaks

* initial sync

* thumbnail file management

* clean up logs and use saved thumbnail on frontend

* publish mqtt messages

* webpush changes to enable trigger notifications

* add enabled switch

* add triggers from explore

* renaming and deletion fixes

* fix typing

* UI updates and add last triggering event time and link

* log exception instead of return in endpoint

* highlight entry in UI when triggered

* save and delete thumbnails directly

* remove alert action for now and add descriptions

* tweaks

* clean up

* fix types

* docs

* docs tweaks

* docs

* reuse enum

web/public/locales/en/views/explore.json

@@ -175,6 +175,10 @@
       "label": "Find similar",
       "aria": "Find similar tracked objects"
     },
+    "addTrigger": {
+      "label": "Add trigger",
+      "aria": "Add a trigger for this tracked object"
+    },
     "audioTranscription": {
       "label": "Transcribe",
       "aria": "Request audio transcription"