refactor: Modularize CSS and fix theme-aware text colors

CSS Restructuring:
- Reorganize monolithic main.css into modular architecture
- Create foundation/ (reset, variables, typography, themes)
- Create layout/ (container, page, grid, paper)
- Create components/ (8 component files)
- Create interactive/ (toggles, remaining for future split)
- Create effects/ (skeleton loading)
- Create contexts/ (print styles)

Theme Support Fixes:
- Replace all hardcoded text colors with CSS variables
- Fix .section-title: rgb(51,51,51) → var(--text-primary)
- Fix .cv-name, .intro-text: hardcoded → theme-aware
- Fix .experience-period, .duration-text: #555/#aaa → variables
- Fix course/project/experience text colors
- Support proper light/dark theme text contrast

Icon & Layout Fixes:
- Standardize all icon sizes to 80×80px
- Change all icon backgrounds to transparent
- Fix award section layout (missing flexbox)
- Update HTML templates (experience.html, awards.html) to width='80'
- Fix default icon sizing conflicts

View Switcher Fix:
- Fix toggleTheme() to target .cv-container instead of body
- Ensures clean/default theme toggle works correctly

Files: 40+ CSS files modularized, 3 templates updated, 7 tests added

templates/partials/sections/experience.html

@@ -15,9 +15,9 @@
         <div class="experience-item">
             <div class="company-logo">
                 {{if .CompanyLogo}}
-                <img src="/static/images/companies/{{.CompanyLogo}}" alt="{{.Company}} logo" onerror="this.parentElement.innerHTML='<iconify-icon icon=\'mdi:office-building\' width=\'60\' height=\'60\' class=\'default-company-icon\'></iconify-icon>'">
+                <img src="/static/images/companies/{{.CompanyLogo}}" alt="{{.Company}} logo" onerror="this.parentElement.innerHTML='<iconify-icon icon=\'mdi:office-building\' width=\'80\' height=\'80\' class=\'default-company-icon\'></iconify-icon>'">
                 {{else}}
-                <iconify-icon icon="mdi:office-building" width="60" height="60" class="default-company-icon"></iconify-icon>
+                <iconify-icon icon="mdi:office-building" width="80" height="80" class="default-company-icon"></iconify-icon>
                 {{end}}
             </div>
             <div class="experience-content">