feat: implement disk resize in LXC settings

[michelroegl-brunner]

Summary

This PR implements automatic disk resizing when changing LXC disk size in the settings modal, along with a complete modal flow redesign and robust error handling.

Features Added

🔧 Disk Resize Functionality

• Automatic disk resizing: When changing disk size in LXC settings, the actual disk is now resized automatically
• Size validation: Only allows increasing disk size for safety
• Multiple resize methods: Primary pct resize command with LVM fallback (lvresize, resize2fs/xfs_growfs)
• Configuration rollback: If resize fails, the configuration file is automatically rolled back

🎨 Improved Modal Flow

• Confirmation Modal: User confirms disk resize operation
• Loading Modal: Shows spinner during processing with descriptive text
• Result Modal: Separate success/error modal that doesn't close automatically
• Settings Modal: Reopens with updated values after result modal closes
• Clean UI: Removed success/error banners from settings modal

🐛 Enhanced Error Handling

• Better error detection: Now checks both exit code AND error output from commands
• Detailed error messages: Captures and displays specific error details (e.g., "Insufficient free space")
• Error propagation: Proper error flow from SSH commands through to UI
• Debug logging: Added comprehensive logging for troubleshooting

🎨 UI/UX Improvements

• Semantic colors: Updated modal styling to use CSS custom properties for proper dark mode support
• Consistent styling: Result modals now match the application's design system
• Responsive design: Proper mobile and tablet support
• Data refresh: Settings modal shows updated values after successful operations

Technical Details

Backend Changes (installedScripts.ts)

• Added parseRootfsStorage() helper to parse storage pool and disk ID
• Added extractSizeInGB() helper for size conversion
• Enhanced resizeDisk() function with proper error detection
• Added tryLVMResize() fallback method
• Implemented configuration rollback mechanism

Frontend Changes (LXCSettingsModal.tsx)

• Added new state management for modal flow
• Updated save mutation handlers for new flow
• Added result modal component with proper styling
• Implemented data refresh after operations
• Removed banner-based notifications

Error Detection Fix

The main bug fix addresses the issue where pct resize returns exit code 0 even when it fails with "Insufficient free space". The solution checks both:

• Exit code (0 = success, non-zero = failure)
• Error output content (looks for "error" or "insufficient" keywords)

Testing

• ✅ Successful disk resize (11G → 12G)
• ✅ Error handling for insufficient space
• ✅ Configuration rollback on failure
• ✅ Proper modal flow and user feedback
• ✅ Dark mode styling consistency