Major improvements: rollbacks, testing, docs, and code quality

- Fixed rollback implementation with two-phase approach (remove new, downgrade upgraded)
- Added explicit package tracking (newly_installed vs upgraded)
- Implemented graceful error handling with fail-fast approach
- Added comprehensive test suite (20 tests across 3 test files)
- Created centralized APT command execution module (apt_commands.rs)
- Added configuration system with dry-run, quiet, and APT options
- Reduced code duplication and improved maintainability
- Added extensive documentation (rollbacks.md, rollbacks-not-featured.md, ffi-bridge.md)
- Created configuration usage example
- Updated README with crate usage instructions
- All tests passing, clean compilation, production-ready

examples/configuration_usage.rs

@@ -0,0 +1,77 @@
+//! Example demonstrating APT wrapper configuration options
+//! 
+//! This example shows how to use the various configuration options
+//! available in the APT wrapper.
+
+use apt_wrapper::{AptTransaction, AptConfig, init};
+
+fn main() -> Result<(), Box<dyn std::error::Error>> {
+    println!("=== APT Wrapper Configuration Example ===");
+    
+    // Initialize
+    init()?;
+    println!("✓ APT wrapper initialized");
+    
+    // Example 1: Default configuration
+    println!("\n--- Example 1: Default Configuration ---");
+    let mut tx1 = AptTransaction::new()?;
+    tx1.add_package("apt")?;
+    println!("✓ Created transaction with default config");
+    println!("  Config: {:?}", tx1.config());
+    
+    // Example 2: Custom configuration
+    println!("\n--- Example 2: Custom Configuration ---");
+    let config = AptConfig {
+        no_install_recommends: true,
+        no_install_suggests: true,
+        assume_yes: true,
+        quiet: false,
+        dry_run: true,
+    };
+    
+    let mut tx2 = AptTransaction::with_config(config)?;
+    tx2.add_package("curl")?;
+    println!("✓ Created transaction with custom config");
+    println!("  Config: {:?}", tx2.config());
+    
+    // Example 3: Testing configuration
+    println!("\n--- Example 3: Testing Configuration ---");
+    let mut tx3 = AptTransaction::for_testing()?;
+    tx3.add_package("vim")?;
+    println!("✓ Created transaction for testing");
+    println!("  Config: {:?}", tx3.config());
+    
+    // Example 4: Runtime configuration changes
+    println!("\n--- Example 4: Runtime Configuration Changes ---");
+    let mut tx4 = AptTransaction::new()?;
+    tx4.add_package("git")?;
+    
+    // Enable dry run mode
+    tx4.enable_dry_run();
+    println!("✓ Enabled dry run mode");
+    
+    // Enable quiet mode
+    tx4.enable_quiet();
+    println!("✓ Enabled quiet mode");
+    
+    // Disable dry run mode
+    tx4.disable_dry_run();
+    println!("✓ Disabled dry run mode");
+    
+    println!("  Final config: {:?}", tx4.config());
+    
+    // Example 5: Configuration validation
+    println!("\n--- Example 5: Configuration Validation ---");
+    let mut tx5 = AptTransaction::new()?;
+    tx5.add_package("apt")?;
+    
+    // Resolve dependencies (this will validate packages exist)
+    tx5.resolve()?;
+    println!("✓ Dependencies resolved successfully");
+    
+    // Note: We don't actually commit in examples to avoid installing packages
+    println!("\n=== Example completed ===");
+    println!("Note: Transactions were not committed to avoid installing packages");
+    
+    Ok(())
+}