feat(ai): 添加 SeaORM Entity (ai_prompt/ai_analysis/ai_usage)

Co-Authored-By: Claude Opus 4.7 <noreply@anthropic.com>

crates/erp-ai/src/entity/ai_usage.rs

@@ -0,0 +1,24 @@
+use sea_orm::entity::prelude::*;
+use serde::{Deserialize, Serialize};
+
+#[derive(Clone, Debug, PartialEq, DeriveEntityModel, Serialize, Deserialize)]
+#[sea_orm(table_name = "ai_usage_logs")]
+pub struct Model {
+    #[sea_orm(primary_key, auto_increment = false)]
+    pub id: Uuid,
+    pub tenant_id: Uuid,
+    pub provider: String,
+    pub model: String,
+    pub analysis_type: String,
+    pub input_tokens: i32,
+    pub output_tokens: i32,
+    pub duration_ms: i32,
+    pub cost_cents: i32,
+    pub is_cache_hit: bool,
+    pub created_at: DateTimeUtc,
+}
+
+#[derive(Copy, Clone, Debug, EnumIter, DeriveRelation)]
+pub enum Relation {}
+
+impl ActiveModelBehavior for ActiveModel {}