feat: add Deepgram audio transcription

Co-authored-by: Safzan Pirani <safzanpirani@users.noreply.github.com>

docs/nodes/audio.md

@@ -62,8 +62,24 @@ read_when:
 }
 ```
 
+### Provider-only (Deepgram)
+```json5
+{
+  tools: {
+    media: {
+      audio: {
+        enabled: true,
+        models: [{ provider: "deepgram", model: "nova-3" }]
+      }
+    }
+  }
+}
+```
+
 ## Notes & limits
 - Provider auth follows the standard model auth order (auth profiles, env vars, `models.providers.*.apiKey`).
+- Deepgram picks up `DEEPGRAM_API_KEY` when `provider: "deepgram"` is used.
+- Deepgram setup details: [Deepgram (audio transcription)](/providers/deepgram).
 - Default size cap is 20MB (`tools.media.audio.maxBytes`). Oversize audio is skipped for that model and the next entry is tried.
 - Default `maxChars` for audio is **unset** (full transcript). Set `tools.media.audio.maxChars` or per-entry `maxChars` to trim output.
 - Use `tools.media.audio.attachments` to process multiple voice notes (`mode: "all"` + `maxAttachments`).