Add vision model support and related configurations in Assistant

- Introduce new fields in AssistantConfig, schemas, and database models to support vision capabilities, including `vision_enabled` and `vision_model_resource_id`.
- Enhance validation logic in routes to ensure proper handling of vision models and their requirements.
- Update the AssistantPage and related frontend components to include options for enabling vision understanding and selecting appropriate vision models.
- Modify database seed scripts to include vision-related data for assistants, ensuring consistent setup.
- Refactor related functions to integrate vision model handling in the audio-visual processing pipeline.

Makefile

@@ -7,7 +7,7 @@
 PSQL = docker compose exec -T postgres psql -U postgres -d postgres
 
 .DEFAULT_GOAL := help
-.PHONY: help up down restart logs api-logs db db-list db-seed db-seed-model-resources db-seed-assistants db-clear db-reset
+.PHONY: help up down restart logs api-logs db db-list db-init db-seed db-seed-model-resources db-seed-assistants db-clear db-reset
 
 help: ## 列出所有可用目标
 	@grep -E '^[a-zA-Z_-]+:.*?## .*$$' $(MAKEFILE_LIST) \
@@ -33,6 +33,11 @@ api-logs: ## 只看后端日志
 db: ## 进入交互式 psql
 	docker compose exec postgres psql -U postgres -d postgres
 
+db-init: ## 启动 API 并等待建表完成(表由 init_db/create_all 在 API 启动时创建)
+	docker compose up -d postgres api
+	@echo "Waiting for API health (schema init)..."
+	@until docker compose exec -T api python -c "import urllib.request; urllib.request.urlopen('http://localhost:8000/health')" 2>/dev/null; do sleep 1; done
+
 db-list: ## 列出模型资源与助手
 	@$(PSQL) -c "SELECT id, name, capability, interface_type, is_default FROM model_resources ORDER BY id;"
 	@$(PSQL) -c "SELECT id, name, type FROM assistants ORDER BY id;"
@@ -43,9 +48,9 @@ db-seed-model-resources: ## 灌入 12 条模型资源种子(幂等)
 db-seed-assistants: ## 灌入 知识库 + 助手 种子(幂等;依赖模型资源已就绪)
 	$(PSQL) < backend/db/seed_assistants.sql
 
-db-seed: db-seed-model-resources db-seed-assistants ## 全量灌种子(模型资源→知识库→助手,幂等,可重复执行)
+db-seed: db-init db-seed-model-resources db-seed-assistants ## 全量灌种子(模型资源→知识库→助手,幂等,可重复执行)
 
-db-clear: ## 清空 助手/知识库/模型资源(按依赖顺序)
-	$(PSQL) -c "TRUNCATE assistant_model_bindings, assistants, knowledge_bases, model_resources CASCADE;"
+db-clear: ## 清空 助手/知识库/模型资源(按依赖顺序;表不存在时跳过)
+	@$(PSQL) -c "DO \$$\$$ BEGIN IF EXISTS (SELECT FROM pg_tables WHERE schemaname = 'public' AND tablename = 'model_resources') THEN TRUNCATE assistant_model_bindings, assistants, knowledge_bases, model_resources CASCADE; END IF; END \$$\$$;"
 
-db-reset: db-clear db-seed ## 清空后重新灌全部种子
+db-reset: db-init db-clear db-seed ## 清空后重新灌全部种子(空库时仅建表+灌种)