Revert "fix: switch embedding dimension from 1536 to 2560 for qwen-embedding-4b"

This reverts commit e09ea3a145.

memento-note/app/api/admin/embeddings/validate/route.ts

@@ -35,7 +35,7 @@ export async function GET() {
     const invalidResult: Array<{ count: bigint }> = await prisma.$queryRawUnsafe(
       `SELECT COUNT(*)::bigint as count FROM "NoteEmbedding" e
        WHERE e."embedding" IS NULL
-          OR array_length(string_to_array(replace(replace(e."embedding"::text, '[', ''), ']', ''), ','), 1) != 2560`
+          OR array_length(string_to_array(replace(replace(e."embedding"::text, '[', ''), ']', ''), ','), 1) != 1536`
     )
     const invalidCount = Number(invalidResult[0]?.count ?? 0)