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>

README.md

@@ -80,8 +80,7 @@ The service is configured through the `config.json` file:
     "return_timestamps": false,
     "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": 1.25
+    "compand_params": "0.3,1 -90,-90,-70,-50,-40,-15,0,0 -7 0 0.15"
 }
 ```
 
@@ -101,7 +100,6 @@ The service is configured through the `config.json` file:
 | `audio_rate` | Audio sampling rate in Hz |
 | `norm_level` | Normalization level for audio preprocessing |
 | `compand_params` | Parameters for audio compression/expansion |
-| `audio_speed_factor` | Audio speed factor for faster recognition (1.0 = no speedup, 1.25 = 25% faster) |
 
 ## Web interface