cleanup: remove dead code and duplicate docs

- Remove session-ses_2f27.md (161KB raw session log)
- Remove 49 ROOT_* duplicate files across REFERENCE/
- Remove 14 duplicate files between REFERENCE/ root and history/
- Remove asr_legacy.rs (dead code, replaced by asr.rs)
- Remove src/core/worker/ (duplicate JobWorker)
- Remove src/core/layers/ (empty directory)
- Remove 4 .bak files in src/
- Remove 7 dead private methods in worker/processor.rs
- Remove backup directory from git tracking

scripts/test_pyannote_multilingual.py

@@ -14,7 +14,6 @@ except Exception as e:
 
 # 2. 檢查模型
 try:
-    from pyannote.audio import Pipeline
     print("✅ Pipeline 導入成功")
     
     # 檢查可用模型