feat: add backend API endpoints for highlights and cross-references

🤖 Generated with [Claude Code](https://claude.com/claude-code)

Co-Authored-By: Claude <noreply@anthropic.com>

app/api/highlights/all/route.ts

@@ -0,0 +1,42 @@
+import { NextResponse } from 'next/server'
+import { prisma } from '@/lib/db'
+import { getAuth } from '@clerk/nextjs/server'
+
+export const runtime = 'nodejs'
+
+export async function GET(request: Request) {
+  try {
+    const { userId } = await getAuth(request)
+    if (!userId) {
+      return NextResponse.json({ error: 'Unauthorized' }, { status: 401 })
+    }
+
+    const highlights = await prisma.userHighlight.findMany({
+      where: { userId },
+      select: {
+        id: true,
+        verseId: true,
+        color: true,
+        createdAt: true,
+        updatedAt: true
+      }
+    })
+
+    return NextResponse.json({
+      highlights: highlights.map(h => ({
+        id: h.id,
+        verseId: h.verseId,
+        color: h.color,
+        createdAt: h.createdAt.getTime(),
+        updatedAt: h.updatedAt.getTime()
+      })),
+      serverTime: Date.now()
+    })
+  } catch (error) {
+    console.error('Error fetching highlights:', error)
+    return NextResponse.json(
+      { error: 'Failed to fetch highlights' },
+      { status: 500 }
+    )
+  }
+}