fix: remove fallback content, fix video upload and positioning

- Remove hardcoded fallback data — DB is sole content source
- Sections render conditionally when data exists
- Hero video slots save after each upload (not only when all 3 filled)
- Video positions preserved (left/center/right) with empty string slots
- Client-side 10MB hard limit on video uploads with clear error
- Server-side upload error handling for body size limits
- Guard Team section against empty members array
- Clean up old uploaded images and videos

src/components/sections/Hero.tsx

@@ -20,9 +20,10 @@ export function Hero({ data: hero }: HeroProps) {
   const overlayRef = useRef<HTMLDivElement>(null);
   const readyCount = useRef(0);
   const [mounted, setMounted] = useState(false);
-  const videos = hero.videos?.length ? hero.videos : DEFAULT_VIDEOS;
-  const centerVideo = videos[Math.floor(videos.length / 2)] || videos[0];
-  const totalVideos = videos.slice(0, 3).length + 1; // desktop (3) + mobile (1)
+  const hasVideos = hero.videos?.some(Boolean);
+  const videos = hasVideos ? hero.videos! : DEFAULT_VIDEOS;
+  const centerVideo = videos[1] || videos[0];
+  const totalVideos = videos.slice(0, 3).filter(Boolean).length + 1; // desktop (filled) + mobile (1)
 
   const prefersReducedMotion = useRef(false);
 
@@ -106,6 +107,7 @@ export function Hero({ data: hero }: HeroProps) {
           {/* Desktop: diagonal split with all videos */}
           <div className="absolute inset-0 hidden md:block">
             {videos.slice(0, 3).map((src, i) => {
+              if (!src) return null;
               const positions = [
                 { left: "0%", width: "38%" },
                 { left: "31%", width: "38%" },
@@ -118,7 +120,7 @@ export function Hero({ data: hero }: HeroProps) {
               ];
               return (
                 <div
-                  key={src}
+                  key={`video-${i}`}
                   className="absolute top-0 bottom-0 overflow-hidden"
                   style={{
                     left: positions[i].left,