polish: nav scroll threshold, footer cleanup, hero gradient

- Nav: trigger solid background at 10px scroll (was 100px) to prevent logo/text overlap
- Footer: copyright uses legal name "LetsBe Solutions LLC"
- Footer: location changed to "American-founded. Serving the Côte d'Azur and beyond."
- Footer: remove GitHub social link (no public GitHub)
- Hero: smooth gradient fade into trust bar section (no hard color gap)
- Services: "SEO & Digital Marketing" replaces "SEO & Performance"

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

src/components/sections/Hero.tsx

@@ -341,10 +341,10 @@ export default function Hero() {
 
       {/* ─── Bottom fade into next section ────────────────────────────── */}
       <div
-        className="absolute bottom-0 left-0 right-0 h-28 pointer-events-none z-10"
+        className="absolute bottom-0 left-0 right-0 h-40 pointer-events-none z-10"
         style={{
           background:
-            'linear-gradient(to bottom, transparent, rgba(248,249,250,0.65))',
+            'linear-gradient(to bottom, transparent, #f3f4f5)',
         }}
         aria-hidden="true"
       />

src/components/sections/TrustBar.tsx

@@ -113,11 +113,11 @@ export default function TrustBar() {
       aria-label="Trust indicators"
       className="relative bg-surface-low py-12"
     >
-      {/* Gradient bridge — blends hero surface-high into this section */}
+      {/* Gradient bridge — blends hero into this section */}
       <div
-        className="absolute top-0 left-0 right-0 h-16 pointer-events-none"
+        className="absolute top-0 left-0 right-0 h-24 pointer-events-none"
         style={{
-          background: 'linear-gradient(to bottom, #ffffff, transparent)',
+          background: 'linear-gradient(to bottom, #f8f9fa, transparent)',
         }}
         aria-hidden="true"
       />