feat: enhance shortcuts modal and complete logos-to-icons rename

This commit includes graphical keyboard icons integration, modal styling
improvements, and comprehensive "Logos" to "Icons" terminology update.

Changes:
- Add graphical keyboard icons using Iconify MDI (Tab, Ctrl, Cmd, Esc, etc.)
- Implement color scheme: black title, green subtitle/headers, blue kbd elements
- Add visual boxes with borders and shadows for section grouping
- Change modal from 3-column to 2-column grid layout (900px width)
- Fix critical bug: all 5 sections now render (was only showing 2)

Rename "Logos" to "Icons" across entire codebase:
- Go models: ToggleLogos → ToggleIcons, ShowLogos → ShowIcons
- Routes: /toggle/logos → /toggle/icons
- Templates: desktop-logo-toggle → desktop-icon-toggle, #logoToggle → #iconToggle
- JavaScript: logoToggles → iconToggles, sync logic updated
- CSS: .show-logos → .show-icons
- UI JSON: toggleLogos → toggleIcons
- Comments and labels updated

Technical details:
- Rebuilt Go binary to fix template rendering error
- Fixed JSON struct tag: json:"toggleLogos" → json:"toggleIcons"
- Updated kbd element styling for icon alignment (inline-flex)
- Added margin-bottom to subtitle (0.5rem)
- Grid now 2 columns for better 5-section layout

All 5 sections now render correctly:
1. Zoom Control
2. View Controls
3. Navigation
4. Actions
5. Browser Defaults

data/ui-en.json

@@ -36,9 +36,9 @@
           "key": "Tab to Length",
           "description": "Toggle CV length (Short/Long)"
         },
-        "toggleLogos": {
-          "key": "Tab to Logos",
-          "description": "Show/hide company logos"
+        "toggleIcons": {
+          "key": "Tab to Icons",
+          "description": "Show/hide company icons"
         },
         "toggleTheme": {
           "key": "Tab to View",

data/ui-es.json

@@ -36,9 +36,9 @@
           "key": "Tab a Longitud",
           "description": "Alternar longitud CV (Corto/Largo)"
         },
-        "toggleLogos": {
-          "key": "Tab a Logos",
-          "description": "Mostrar/ocultar logos de empresas"
+        "toggleIcons": {
+          "key": "Tab a Iconos",
+          "description": "Mostrar/ocultar iconos de empresas"
         },
         "toggleTheme": {
           "key": "Tab a Vista",