feat: add Guided Learning Paths feature

Implement PathManager to orchestrate multi-module learning journeys:
- Add PathManager class with start/pause/resume functionality
- Create learning-paths.json config with CSS Fundamentals path
- Integrate path progress tracking with LessonEngine
- Add path selection UI to homepage and navigation
- Include JSON schema for learning path validation
- Add comprehensive test suite for PathManager

.auto-claude-status

@@ -0,0 +1,25 @@
+{
+  "active": true,
+  "spec": "002-guided-learning-paths",
+  "state": "building",
+  "subtasks": {
+    "completed": 15,
+    "total": 21,
+    "in_progress": 1,
+    "failed": 0
+  },
+  "phase": {
+    "current": "App Integration",
+    "id": 4,
+    "total": 4
+  },
+  "workers": {
+    "active": 0,
+    "max": 1
+  },
+  "session": {
+    "number": 119,
+    "started_at": "2026-01-11T04:33:49.649857"
+  },
+  "last_update": "2026-01-11T14:52:20.837371"
+}