feat(ai): 补全 Prompt CRUD + 分析历史 + 用量统计 handler 和路由

- 替换 list_analysis/get_analysis 空壳为真实查询
- 新增 list_prompts/create_prompt/activate_prompt/rollback_prompt
- 新增 usage_overview/usage_by_type
- 注册 6 个新路由到 AiModule

crates/erp-ai/src/module.rs

@@ -104,5 +104,29 @@ impl AiModule {
                 "/ai/analysis/{id}",
                 axum::routing::get(crate::handler::get_analysis),
             )
+            .route(
+                "/ai/prompts",
+                axum::routing::get(crate::handler::list_prompts),
+            )
+            .route(
+                "/ai/prompts",
+                axum::routing::post(crate::handler::create_prompt),
+            )
+            .route(
+                "/ai/prompts/{id}/activate",
+                axum::routing::post(crate::handler::activate_prompt),
+            )
+            .route(
+                "/ai/prompts/{id}/rollback",
+                axum::routing::post(crate::handler::rollback_prompt),
+            )
+            .route(
+                "/ai/usage/overview",
+                axum::routing::get(crate::handler::usage_overview),
+            )
+            .route(
+                "/ai/usage/by-type",
+                axum::routing::get(crate::handler::usage_by_type),
+            )
     }
 }