feat: add course logo support with servoy, forem, and camaracomercio logos

- Add courseLogo field to Course struct in Go
- Update template to display course logos with fallback to school icon
- Add CSS styling for course logo images (80x80px, contained, bordered)
- Add logos to three courses in both English and Spanish:
  * Servoy World 2011 (servoy.png)
  * Train the Trainers / Formador de Formadores (forem.png)
  * Windows 2003 Server (camaracomercio.png)
- Course logos stored in /static/images/courses/ folder
- Similar implementation to project logos with error handling

data/cv-en.json

@@ -667,6 +667,7 @@
     {
       "title": "Servoy World 2011",
       "institution": "Servoy",
+      "courseLogo": "servoy.png",
       "location": "Amsterdam",
       "date": "2011-02",
       "duration": "3 days",
@@ -680,6 +681,7 @@
     {
       "title": "Train the Trainers",
       "institution": "FOREM Extremadura",
+      "courseLogo": "forem.png",
       "location": "Cáceres",
       "date": "2009-06",
       "duration": "150 hours",
@@ -693,6 +695,7 @@
     {
       "title": "Windows 2003 Server",
       "institution": "Cáceres Chamber of Commerce",
+      "courseLogo": "camaracomercio.png",
       "location": "Cáceres",
       "date": "2006-01",
       "duration": "80 hours",