Summarize tone: re-summarize in a chosen voice (backend)

POST /reprocess?job=summarize&tone=<voice> persists the voice on the job
row (queue carries only ids, so a sweep re-enqueue keeps it), the LLM
prompt appends 'write every field in a <tone> tone — the tone colors
the wording, never the facts', and the resulting summary records its
tone (SummaryOut.tone). Plain re-summarize clears a previous tone.
Migration tone0000000001 (summaries.tone, processing_jobs.tone).
78 passed, 1 skipped; ruff clean.

backend/tests/test_ai_pipeline.py

@@ -95,7 +95,7 @@ class FakeLlm:
         self.fail = fail
         self.seen = []
 
-    async def summarize(self, transcript, *, title=None):
+    async def summarize(self, transcript, *, title=None, tone=None):
         self.seen.append(transcript)
         if self.fail is not None:
             raise self.fail