feat: 配置加载 config（三 yaml + env 优先级 + 脱敏）

tests/fixtures/app.yaml

@@ -0,0 +1,7 @@
+server:
+  max_upload_mb: 10
+session:
+  sqlite_path: "C:/tmp/genesis.db"
+task_queue:
+  backend: memory
+  timeout_sec: 300

tests/fixtures/inference.yaml

@@ -0,0 +1,8 @@
+models:
+  primary:
+    provider: deepseek
+    name: deepseek-chat
+llm_calls:
+  max_context_tokens: 16000
+structured_output:
+  max_parse_retry: 3

tests/fixtures/rag.yaml

@@ -0,0 +1,9 @@
+embedding:
+  model: BAAI/bge-small-zh-v1.5
+vector_store:
+  adapter: chroma
+  qdrant:
+    url: http://qdrant:6333
+    api_key: ${QDRANT_API_KEY}
+retrieval:
+  rrf_k: 42