支持学生头像设置与展示（上传/清除）

src/utils/studentAvatar.ts

@@ -0,0 +1,47 @@
+export const getAvatarFromExtraJson = (extraJson?: string | null): string | null => {
+  if (!extraJson) return null
+
+  try {
+    const parsed = JSON.parse(extraJson)
+    if (!parsed || typeof parsed !== "object") return null
+
+    const avatar = (parsed as Record<string, unknown>).avatar
+    if (typeof avatar !== "string") return null
+
+    const trimmed = avatar.trim()
+    if (!trimmed) return null
+
+    if (trimmed.startsWith("data:image/")) return trimmed
+    if (trimmed.startsWith("http://") || trimmed.startsWith("https://")) return trimmed
+
+    return null
+  } catch {
+    return null
+  }
+}
+
+export const setAvatarInExtraJson = (
+  extraJson: string | null | undefined,
+  avatar: string | null
+): string => {
+  let base: Record<string, unknown> = {}
+
+  if (extraJson) {
+    try {
+      const parsed = JSON.parse(extraJson)
+      if (parsed && typeof parsed === "object") {
+        base = parsed as Record<string, unknown>
+      }
+    } catch {
+      base = {}
+    }
+  }
+
+  if (avatar && avatar.trim()) {
+    base.avatar = avatar.trim()
+  } else {
+    delete base.avatar
+  }
+
+  return JSON.stringify(base)
+}