feat: restructure learning path with new modules and enhanced explanations

- Add CSS Colors, Typography, Advanced Selectors, and Grid modules
- Remove deprecated HTML Marquee module from all languages
- Remove redundant div & span lesson from HTML Block & Inline
- Move SVG module from HTML to CSS section
- Enhance first lessons with comprehensive explanations:
  - Flexbox: historical context, axes concept
  - Colors: named colors, background-color explained
  - Grid: comparison to Flexbox, key properties
- Swap header logo highlight (CRISPIES instead of CODE)
- Use English fallbacks for new modules in non-EN languages
- Fix test to include 'playground' mode

New path: 19 modules (~78 lessons) vs previous 16 modules (62 lessons)

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

src/main.css

@@ -186,6 +186,10 @@ kbd {
 }
 
 .logo h1 .code-text {
+	color: var(--primary-color);
+}
+
+.logo h1 .crispies-text {
 	background: var(--primary-color);
 	color: white;
 	padding: 0.15rem 0.35rem;
@@ -194,10 +198,6 @@ kbd {
 	box-shadow: 0 2px 4px rgba(0, 0, 0, 0.15);
 }
 
-.logo h1 span:last-child {
-	color: var(--primary-color);
-}
-
 .help-toggle {
 	width: 28px;
 	height: 28px;