feat: Implement speaker analysis and EPUB 3 export functionality

- Added speaker analysis module to infer speaker identities from text chunks.
- Introduced SpeakerGuess and SpeakerAnalysis data classes for managing speaker data.
- Developed functions for analyzing speaker occurrences and confidence levels.
- Created EPUB 3 exporter to generate EPUB packages with synchronized narration and media overlays.
- Implemented configurable chunking options for TTS synthesis and EPUB alignment.
- Enhanced JavaScript for speaker preview functionality in the web interface.
- Added comprehensive tests for chunking and EPUB exporting features.
- Documented upgrade plan for transitioning to EPUB 3 with multi-speaker support.

tests/test_service.py

@@ -54,4 +54,8 @@ def test_service_processes_job(tmp_path):
     assert runner_invocations, "conversion runner was never called"
     assert job.status is JobStatus.COMPLETED
     assert job.progress == 1.0
-    assert job.result.audio_path == outputs / f"{job.id}.wav"
+    assert job.result.audio_path == outputs / f"{job.id}.wav"
+    assert job.chunk_level == "paragraph"
+    assert job.speaker_mode == "single"
+    assert job.chunks == []
+    assert not job.generate_epub3