feat(ai): 知识库 V2 集成 — 多知识源路由 + AI 分析自动注入

- KnowledgeV2Source: 实现 KnowledgeSource trait，自动搜索所有启用的知识库
- AnalysisService.knowledge_sources: 改 Option → Vec 支持多知识源
- 最佳匹配策略：遍历所有知识源取最高 confidence 的上下文注入 system prompt
- main.rs 共享 EmbeddingService + KnowledgeV2Service 实例

Phase 2 Task 12-15

crates/erp-server/src/main.rs

@@ -568,12 +568,26 @@ async fn main() -> anyhow::Result<()> {
             }
         }
 
+        let embedding_svc = std::sync::Arc::new(
+            erp_ai::service::embedding::EmbeddingService::from_settings(&db).await,
+        );
+        let knowledge_v2_svc = std::sync::Arc::new(
+            erp_ai::service::knowledge_v2::KnowledgeV2Service::new(db.clone()),
+        );
+
         let analysis_svc =
             erp_ai::service::analysis::AnalysisService::new(registry.clone(), db.clone())
                 .with_knowledge_source(std::sync::Arc::new(
                     erp_ai::knowledge::structured_source::StructuredKnowledgeSource::new(
                         db.clone(),
                     ),
+                ))
+                .with_knowledge_source(std::sync::Arc::new(
+                    erp_ai::knowledge::v2_source::KnowledgeV2Source::new(
+                        db.clone(),
+                        knowledge_v2_svc.clone(),
+                        embedding_svc.clone(),
+                    ),
                 ));
         let analysis = std::sync::Arc::new(analysis_svc);
         let prompt = std::sync::Arc::new(erp_ai::service::prompt::PromptService::new(db.clone()));
@@ -594,13 +608,6 @@ async fn main() -> anyhow::Result<()> {
             cache_ttl,
         ));
 
-        let embedding_svc = std::sync::Arc::new(
-            erp_ai::service::embedding::EmbeddingService::from_settings(&db).await,
-        );
-        let knowledge_v2_svc = std::sync::Arc::new(
-            erp_ai::service::knowledge_v2::KnowledgeV2Service::new(db.clone()),
-        );
-
         erp_ai::AiState {
             db: db.clone(),
             event_bus: event_bus.clone(),