feat: implement storage quota management for uploads

- Added storage quota enforcement for audio and image uploads in the respective routes.
- Introduced reservation system to manage concurrent uploads and prevent quota overages.
- Enhanced comment creation to account for audio and image attachment sizes against user quotas.
- Created new UploadReservation model to track in-flight upload reservations.
- Backfilled existing video assets with size information from R2.
- Added progress component for UI feedback during uploads.
- Updated API responses to include reservation IDs for better quota management.
- Adjusted error handling to return appropriate storage limit exceeded messages.

app/api/settings/storage/route.ts

@@ -0,0 +1,40 @@
+import { auth } from '@/lib/auth';
+import { apiErrors, successResponse, withCacheControl } from '@/lib/api-response';
+import { getUserStorageInfo } from '@/lib/storage-quota';
+import { hasBillingAccess } from '@/lib/billing';
+import { db } from '@/lib/db';
+
+// GET /api/settings/storage
+export async function GET() {
+  const session = await auth();
+  if (!session?.user?.id) {
+    return apiErrors.unauthorized();
+  }
+
+  // Only users with active billing (or on a self-hosted instance where billing
+  // is disabled) should be able to enumerate their storage breakdown.
+  const user = await db.user.findUnique({
+    where: { id: session.user.id },
+    select: {
+      subscriptionStatus: true,
+      trialEndsAt: true,
+      stripeCurrentPeriodEnd: true,
+      billingAccessEndedAt: true,
+    },
+  });
+
+  if (!user || !hasBillingAccess(user)) {
+    return apiErrors.forbidden();
+  }
+
+  const info = await getUserStorageInfo(session.user.id);
+
+  const response = successResponse({
+    usedBytes: info.usedBytes.toString(),
+    limitBytes: info.limitBytes.toString(),
+    percentage: info.percentage,
+  });
+
+  // Cache for 60s — stale data is acceptable for a usage meter
+  return withCacheControl(response, 'private, max-age=60');
+}