feat: add complete sidebar content to match original React CV

Comprehensive update to achieve feature parity with old React implementation.

## Data Layer (Backend)

**Updated Go Models** (internal/models/cv.go):
- Added Course struct (title, institution, location, date, duration, description)
- Added Reference struct (title, URL, type)
- Added Language.Detail field for proficiency descriptions
- Added CV.Courses and CV.References arrays

**Complete Data Population** (data/cv-es.json):
- Added 6 NEW skill categories (42 items):
  * Lenguajes de Programación (11 items: Java, Groovy, PHP, XML, XSLT, ActionScript, Shell, C, C++)
  * Frameworks PHP (4 items: Yii, Zend, WordPress API, Joomla API)
  * Frameworks Java (8 items: Play!, Struts, Spring, Hibernate, Ibatis, Magnolia CMS, XWiki, TESEO)
  * Servidores de Aplicaciones (9 items: Apache, WAMP, MAMP, Tomcat, JBoss, Resin, Jetty, Websphere, Weblogic)
  * CMS y Entornos (6 items: Joomla, WordPress, RapidWeaver, Servoy, WebRatio, Magnolia)
  * Herramientas de Diseño (4 items: Corel, Photoshop, Illustrator, GIMP)

- Updated existing categories with missing items:
  * Ecosistema JavaScript: +Redux, Flux, Gulp, Grunt
  * Desarrollo Web: +JSP, PHP, Handlebars, Moustache, Velocity, Freemarker, jQuery, mooTools, DOM, Ajax, SEO, WebServices
  * Bases de Datos: +Hypersonic, Dominio de SQL
  * Soft Skills: +5 team management items

- Added Catalan language (Comprensión, Level 2)
- Added detail field to all languages (oral/written breakdown)

- Added 4 courses:
  * Servoy World 2011 (Amsterdam, 3 días)
  * Formador de Formadores (FOREM, 150 horas)
  * Windows 2003 Server (Cámara de Comercio, 80 horas)
  * I Jornada Extremeña (Universidad, 3 días)

- Added 8 references:
  * Recommendation letters, portfolios, profiles, CVs

- Fixed driver's license: Tipo C → Tipo B

## Presentation Layer (Frontend)

**Template Updates** (templates/cv-content.html, templates/index.html):
- Skills section: Now renders ALL 13 categories dynamically
- Languages section: Added detail field display
- NEW Courses section: Full course details with institutions
- NEW References section: Clickable links with security attributes
- NEW Other section: Driver's license display
- Responsive grid layout maintained
- Conditional rendering (sections only show if data exists)

**Styling** (static/css/main.css):
- Added .course-item, .course-desc styles
- Added .reference-item, .ref-type styles
- Added .language-detail styles
- Maintained consistent sidebar section styling

## Impact

**Before**: 7 skill categories, 3 languages, 0 courses, 0 references
**After**: 13 skill categories (+6), 4 languages (+1), 4 courses (+4), 8 references (+8)
**Total**: 90+ new data points added

Sidebar now matches original React CV feature-for-feature.

internal/models/cv.go

@@ -18,6 +18,8 @@ type CV struct {
 	Projects       []Project       `json:"projects"`
 	Awards         []Award         `json:"awards"`
 	Certifications []Certification `json:"certifications"`
+	Courses        []Course        `json:"courses"`
+	References     []Reference     `json:"references"`
 	Other          Other           `json:"other"`
 	Meta           Meta            `json:"meta"`
 }
@@ -90,6 +92,7 @@ type Language struct {
 	Language    string `json:"language"`
 	Proficiency string `json:"proficiency"`
 	Level       int    `json:"level"`
+	Detail      string `json:"detail,omitempty"` // Optional detail like "Oral (Medio/Alto) Escrito (Alto)"
 }
 
 type Project struct {
@@ -116,6 +119,21 @@ type Certification struct {
 	Description string `json:"description"`
 }
 
+type Course struct {
+	Title       string `json:"title"`
+	Institution string `json:"institution"`
+	Location    string `json:"location"`
+	Date        string `json:"date"`
+	Duration    string `json:"duration"`
+	Description string `json:"description"`
+}
+
+type Reference struct {
+	Title string `json:"title"`
+	URL   string `json:"url"`
+	Type  string `json:"type"` // "recommendation", "portfolio", "profile", "cv", "presentation"
+}
+
 type Other struct {
 	DriverLicense string `json:"driverLicense"`
 }