style: Extract UI constants and refactor main view rendering (#30)

- [x] Add golangci-lint configuration with gocritic ifElseChain disabled
- [x] Rename error variables to avoid shadowing (createErr, watcherErr, watchErr, etc.)
- [x] Replace `interface{}` with `any` type alias throughout codebase
- [x] Add package-level documentation comments to all internal packages
- [x] Reorder struct fields alphabetically for consistency
- [x] Extract UI constants (terminal dimensions, column widths, colors) to constants.go
- [x] Refactor BubbleTeaUI main view rendering into smaller helper functions
- [x] Simplify nested conditionals and improve code clarity
- [x] Add `isForwardDisabled()` helper method to BubbleTeaUI
- [x] Update file permissions from 0644 to 0600 in config tests
- [x] Add `#nosec` comments and error suppression where appropriate
- [x] Improve test table struct field ordering for readability
- [x] Fix resource parsing in AddForward using strings.SplitN
- [x] Add comprehensive tests for new UI helper functions and constants

internal/ui/wizard_styles.go

@@ -143,7 +143,6 @@ func renderBreadcrumb(parts ...string) string {
 func renderList(items []string, cursor int, prefix string, scrollOffset int) string {
 	var b strings.Builder
 
-	const viewportHeight = 20
 	totalItems := len(items)
 
 	// Show scroll up indicator if there are items above the viewport
@@ -153,7 +152,7 @@ func renderList(items []string, cursor int, prefix string, scrollOffset int) str
 
 	// Calculate visible range
 	start := scrollOffset
-	end := scrollOffset + viewportHeight
+	end := scrollOffset + ViewportHeight
 	if end > totalItems {
 		end = totalItems
 	}