fix: opacity fotos + audit completo + rollback legal pages

- Hero: Maldonado aerial opacity 0.12→0.30
- DifferenceCards: card photo opacity 0.06→0.15
- ProcessSteps: section photo opacity 0.05→0.15
- servicios/[slug] + en mirror: full Tailwind v3→CSS vars migration
- PricingTiers + PricingTiersFeatured: rounded-2xl→glass-card
- en/plans: hardcoded Spanish H1→i18n + reveal
- planes, servicios/index, en/servicios/index: reveal en hero
- legal pages: bg-hds-marfil+text-hds-humo→CSS vars

src/components/ProcessSteps.astro

@@ -19,7 +19,7 @@ const steps = [
   <div class="absolute inset-0 pointer-events-none" style="background: var(--hds-gradient-section);" aria-hidden="true"></div>
 
   <!-- Background photo: team working (very subtle, blurred) -->
-  <div class="absolute inset-0 pointer-events-none" aria-hidden="true" style="opacity: 0.05; backdrop-filter: blur(4px);">
+  <div class="absolute inset-0 pointer-events-none" aria-hidden="true" style="opacity: 0.15; backdrop-filter: blur(4px);">
     <img
       src="/images/photos/hands-typing-coffee-1200x800.webp"
       alt=""