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/app/page.tsx

@@ -33,24 +33,26 @@ export default function HomePage() {
       <ClientShell>
         <Header />
         <main id="main-content">
-          <Hero data={content.hero} />
-          <About
-            data={content.about}
-            stats={{
-              trainers: content.team.members.length,
-              classes: content.classes.items.length,
-              locations: content.schedule.locations.length,
-            }}
-          />
-          <Classes data={content.classes} />
-          <Team data={content.team} schedule={content.schedule.locations} />
-          {openDayData && <OpenDay data={openDayData} popups={content.popups} teamMembers={content.team.members} />}
-          <Schedule data={content.schedule} scheduleConfig={content.scheduleConfig} classItems={content.classes.items} teamMembers={content.team.members} />
-          <Pricing data={content.pricing} />
-          <MasterClasses data={content.masterClasses} regCounts={mcRegCounts} popups={content.popups} />
-          <News data={content.news} />
-          <FAQ data={content.faq} />
-          <Contact data={content.contact} />
+          {content?.hero && <Hero data={content.hero} />}
+          {content?.about && (
+            <About
+              data={content.about}
+              stats={{
+                trainers: content.team?.members?.length ?? 0,
+                classes: content.classes?.items?.length ?? 0,
+                locations: content.schedule?.locations?.length ?? 0,
+              }}
+            />
+          )}
+          {content?.classes && <Classes data={content.classes} />}
+          {content?.team && <Team data={content.team} schedule={content.schedule?.locations} />}
+          {openDayData && content?.popups && <OpenDay data={openDayData} popups={content.popups} teamMembers={content.team?.members ?? []} />}
+          {content?.schedule && <Schedule data={content.schedule} scheduleConfig={content.scheduleConfig} classItems={content.classes?.items ?? []} teamMembers={content.team?.members ?? []} />}
+          {content?.pricing && <Pricing data={content.pricing} />}
+          {content?.masterClasses && <MasterClasses data={content.masterClasses} regCounts={mcRegCounts} popups={content.popups} />}
+          {content?.news && <News data={content.news} />}
+          {content?.faq && <FAQ data={content.faq} />}
+          {content?.contact && <Contact data={content.contact} />}
           <BackToTop />
           <FloatingContact />
         </main>