Add TTS voice deletion, async speech jobs, voice-list cache, ref-seconds name tags

- DELETE /tts/voices/{name}: remove a cloned voice via the llama-swap
  passthrough (upstream chatterbox-tts-api exposes DELETE /voices/{name}).
- POST/GET/DELETE /tts/speech/jobs: durable job flow for long syntheses —
  dispatch returns 202 + job id, the synth queues on the GPU permit instead
  of fast-failing 429, and clients poll for the result (kept ~10 min).
- GET /tts/voices now serves an in-memory cache so listing voices doesn't
  make llama-swap spin up the TTS model (evicting the resident LLM);
  invalidated on create/delete, ?refresh=1 forces an upstream re-query.
- Created voice names are tagged with LLAMA_SWAP_TTS_REF_SECONDS (e.g.
  grandma-30s) so the library shows which ref length produced each clone.

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>

src/ai/mod.rs

@@ -37,8 +37,9 @@ pub use llm_client::{
 pub use ollama::{EMBEDDING_MODEL, OllamaClient};
 pub use sms_client::{SmsApiClient, SmsMessage};
 pub use tts::{
-    create_voice_from_library_handler, create_voice_upload_handler, list_voices_handler,
-    tts_speech_handler,
+    cancel_speech_job_handler, create_speech_job_handler, create_voice_from_library_handler,
+    create_voice_upload_handler, delete_voice_handler, list_voices_handler,
+    speech_job_status_handler, tts_speech_handler,
 };
 
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