Fix code review issues: security, race conditions, resource leaks

- Fix race condition: pass return_timestamps as parameter instead of mutating shared state
- Remove /local/transcriptions endpoint (path traversal vulnerability)
- Add timeout=30 and URL scheme validation to prevent SSRF
- Add temp file cleanup via try/finally in all route handlers
- AsyncTaskManager: add threading.Lock and TTL cleanup for completed tasks
- Change audio_rate to 16000 (matches Whisper's expected sample rate)
- Extract filename from URL via Content-Disposition/path
- Detect base64 audio format via python-magic
- Fix response_size_bytes to use json.dumps instead of str()
- Move scipy import to module level
- Clamp temperature to [0.0, 1.0]
- Deduplicate _load_model() code
- Fix docstrings, README structure, typo, log level

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

app/history.py

@@ -1,5 +1,5 @@
 """
-Модуль history_logger.py — сохранение истории транскрибации в JSON-файлы.
+Модуль history.py — сохранение истории транскрибации в JSON-файлы.
 """
 
 import os
@@ -13,7 +13,7 @@ import logging
 logger = logging.getLogger('app.history')
 
 # Корневая директория истории (относительно корня проекта)
-_history_root = os.path.join(os.path.dirname(os.path.dirname(os.path.dirname(__file__))), "history")
+_history_root = os.path.join(os.path.dirname(os.path.dirname(__file__)), "history")
 
 
 def save_history(result: Dict[str, Any], original_filename: str, config: Dict) -> Optional[str]: