fix: Replace ALL remaining hardcoded #ddd borders with theme variable

Replaced 12 hardcoded borders across 5 files:
- _cv-section.css: 2 borders (company icons)
- _projects.css: 2 borders (project icons)
- _courses.css: 2 borders (course icons)
- _toggles.css: 3 borders (logo containers)
- logo-toggle.css: 3 borders (logo containers)

All icon borders now use var(--icon-border):
- Light theme: #ddd (visible)
- Dark theme: transparent (invisible)

Verified with Playwright: rgba(0,0,0,0) in dark theme

static/css/04-interactive/_toggles.css

@@ -113,7 +113,7 @@
 .award-item {
     margin-bottom: 2.5rem;
     padding-bottom: 2rem;
-    border-bottom: 2px solid #ddd;
+    border-bottom: 2px solid var(--icon-border);
     page-break-inside: avoid;
     display: flex;
     gap: 1.2rem;
@@ -149,7 +149,7 @@
     height: 80px;
     object-fit: contain;
     border-radius: 4px;
-    border: 1px solid #ddd;
+    border: 1px solid var(--icon-border);
     background: transparent;
     padding: 10px;
 }
@@ -164,7 +164,7 @@
     align-items: center;
     justify-content: center;
     border-radius: 4px;
-    border: 1px solid #ddd;
+    border: 1px solid var(--icon-border);
     background: transparent;
     color: #999;
     padding: 10px;