Simplify architecture: remove overengineering, flatten structure

- Remove dead code: cache.py, context_managers.py, decorators.py, flask-limiter
- Replace AudioSource ABC + FakeFile (5 classes) with 4 plain functions
- Replace TempFileManager class with create_temp_file/cleanup_temp_files functions
- Simplify RequestLogger from 233 to 65 lines, remove file reading side-effect
- Convert HistoryLogger and AudioUtils classes to module-level functions
- Remove unused speed_up_audio and audio_speed_factor config
- Flatten single-file directories: shared/, api/, storage/, validation/, async_tasks/, logging/
- Merge logging config + request_logger into single infrastructure/log.py
- Fix request_logging config key (was request_logger)
- Trim CLAUDE.md to high-level only

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

config.json

@@ -11,7 +11,6 @@
     "audio_rate": 8000,
     "norm_level": "-0.55",
     "compand_params": "0.3,1 -90,-90,-70,-50,-40,-15,0,0 -7 0 0.15",
-    "audio_speed_factor": 1.0,
     "device_id": 0,
     "file_validation": {
         "max_file_size_mb": 500,
@@ -19,12 +18,9 @@
         "allowed_mime_types": ["audio/wav", "audio/mpeg", "audio/ogg", "audio/flac", "audio/mp4", "audio/x-m4a", "audio/aac", "audio/webm"]
     },
     "allowed_directories": [],
-    "version": "1.0.0",
     "log_level": "INFO",
     "log_file": "logs/whisper_api.log",
     "request_logging": {
-        "exclude_endpoints": ["/health", "/static"],
-        "sensitive_headers": ["authorization", "cookie", "set-cookie", "proxy-authorization", "x-api-key"],
-        "log_debug": false
+        "exclude_endpoints": ["/health", "/static"]
     }
 }