feat: add environment variable configuration for server settings

Configurable via:
- UPSCALE_PORT (default: 7860)
- UPSCALE_HOST (default: 0.0.0.0)
- UPSCALE_SHARE (default: false)

🤖 Generated with [Claude Code](https://claude.com/claude-code)

Co-Authored-By: Claude <noreply@anthropic.com>

src/config.py

@@ -1,5 +1,6 @@
 """Configuration settings for Real-ESRGAN Web UI."""
 
+import os
 from dataclasses import dataclass, field
 from pathlib import Path
 from typing import Optional
@@ -162,10 +163,10 @@ VIDEO_CODECS: dict[str, VideoCodecConfig] = {
 class AppConfig:
     """Main application configuration."""
 
-    # Server settings
+    # Server settings (configurable via environment variables)
-    server_name: str = "0.0.0.0"
+    server_name: str = os.getenv("UPSCALE_HOST", "0.0.0.0")
-    server_port: int = 7860
+    server_port: int = int(os.getenv("UPSCALE_PORT", "7860"))
-    share: bool = False
+    share: bool = os.getenv("UPSCALE_SHARE", "").lower() in ("true", "1", "yes")
 
     # Queue settings
     max_queue_size: int = 20