feat: Add file download functionality and ASCII art preview for camera snapshots

- Implemented DownloadFile method in client.go to download files with authentication.
- Added ascii.go for converting images to ASCII art with configurable parameters.
- Enhanced main.go to include a new option for capturing and displaying snapshots as ASCII art.
- Introduced non-interactive mode for onvif-cli, allowing command execution via command-line arguments.
- Updated documentation to include usage examples for non-interactive mode and scripting.
- Added error handling and improved user prompts for better user experience.

README.md

@@ -552,15 +552,16 @@ go build -o onvif-cli ./cmd/onvif-cli/
 ```
 📋 Main Menu:
   1. Discover Cameras on Network
-  2. List Network Interfaces
-  3. Connect to Camera
-  4. Device Operations
-  5. Media Operations
-  6. PTZ Operations
-  7. Imaging Operations
+  2. Connect to Camera
+  3. Device Operations
+  4. Media Operations
+  5. PTZ Operations
+  6. Imaging Operations
   0. Exit
 ```
 
+Note: The discovery function now intelligently detects multiple interfaces and shows options only when needed - no separate "List Network Interfaces" menu required.
+
 ### Quick Demo Tool
 
 Lightweight tool for quick testing and demonstration:
@@ -581,18 +582,12 @@ go build -o onvif-quick ./cmd/onvif-quick/
 
 ### Network Interface Selection
 
-Both CLI tools support explicit network interface selection for systems with multiple active interfaces:
+The CLI intelligently handles network interface selection automatically:
+- **Single interface**: Auto-discovery works seamlessly
+- **Multiple interfaces**: Shows interfaces only if auto-discovery fails
+- **Multiple active interfaces**: Tries each one and aggregates results
 
-```bash
-# onvif-cli example
-./onvif-cli
-# Select: 2 (List Network Interfaces)
-# Select: 1 (Discover)
-# Choose: y (Use specific interface)
-# Enter: eth0 or 192.168.1.100
-```
-
-Or use the API programmatically:
+For programmatic usage:
 
 ```go
 opts := &discovery.DiscoverOptions{
@@ -606,6 +601,7 @@ devices, err := discovery.DiscoverWithOptions(ctx, 5*time.Second, opts)
 **See**: 
 - `docs/CLI_NETWORK_INTERFACE_USAGE.md` - Detailed CLI guide
 - `discovery/NETWORK_INTERFACE_GUIDE.md` - API usage examples
+- `DESIGN_REFACTOR.md` - How smart interface detection works
 
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