feat: 新增语音转文字（ASR）功能

- 后端：新增 /api/audio/transcribe 接口，调用 Ollama whisper 进行语音识别
- 前端：新增 AudioTranscribePage.vue 页面，支持 MP3/WAV/M4A/OGG/FLAC 等格式
- 注册路由、工具卡片、智能助手欢迎语更新

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

eai_agentplatform/backend-go/internal/model/question.go

@@ -0,0 +1,20 @@
+package model
+
+import "time"
+
+// Question 题目表
+type Question struct {
+	ID          uint      `gorm:"primaryKey" json:"id"`
+	Domain      string    `gorm:"size:16;not null;index" json:"domain"` // company / product / sales
+	CourseID    *uint     `gorm:"index" json:"course_id"`
+	Type        string    `gorm:"size:16;not null" json:"type"` // single / multiple / judge
+	Stem        string    `gorm:"type:text;not null" json:"stem"`
+	Options     string    `gorm:"type:text;not null" json:"options"` // JSON 数组：["A","B","C"]
+	Answer      string    `gorm:"type:text;not null" json:"answer"`  // JSON 数组：single=[索引] multiple=[索引...] judge=[bool]
+	Explanation string    `gorm:"type:text;default:''" json:"explanation"`
+	Status      string    `gorm:"size:16;not null;default:active;index" json:"status"` // active / inactive
+	CreatedAt   time.Time `json:"created_at"`
+	UpdatedAt   time.Time `json:"updated_at"`
+}
+
+func (Question) TableName() string { return "question" }