Make Backtrader an optional extra

uv.lock

@@ -284,7 +284,6 @@ version = "0.1.0"
 source = { virtual = "." }
 dependencies = [
     { name = "akshare" },
-    { name = "backtrader" },
     { name = "baostock" },
     { name = "click" },
     { name = "matplotlib" },
@@ -293,6 +292,11 @@ dependencies = [
     { name = "pyarrow" },
 ]
 
+[package.optional-dependencies]
+backtrader = [
+    { name = "backtrader" },
+]
+
 [package.dev-dependencies]
 dev = [
     { name = "pytest" },
@@ -301,13 +305,14 @@ dev = [
 [package.metadata]
 requires-dist = [
     { name = "akshare", specifier = ">=1.14.0" },
-    { name = "backtrader", specifier = ">=1.9.76.123" },
+    { name = "backtrader", marker = "extra == 'backtrader'", specifier = ">=1.9.76.123" },
     { name = "baostock", specifier = ">=0.8.8" },
     { name = "click", specifier = ">=8.0.0" },
     { name = "matplotlib", specifier = ">=3.7.0" },
     { name = "pandas", specifier = ">=2.0.0" },
     { name = "pyarrow", specifier = ">=14.0.0" },
 ]
+provides-extras = ["backtrader"]
 
 [package.metadata.requires-dev]
 dev = [{ name = "pytest", specifier = ">=7.0.0" }]