chore: remove iFlow-related modules and dependencies

- Deleted `iflow` provider implementation, including thinking configuration (`apply.go`) and authentication modules.
- Removed iFlow-specific tests, executors, and helpers across SDK and internal components.
- Updated all references to exclude iFlow functionality.

sdk/api/management.go

@@ -18,8 +18,6 @@ type ManagementTokenRequester interface {
 	RequestCodexToken(*gin.Context)
 	RequestAntigravityToken(*gin.Context)
 	RequestKimiToken(*gin.Context)
-	RequestIFlowToken(*gin.Context)
-	RequestIFlowCookieToken(*gin.Context)
 	GetAuthStatus(c *gin.Context)
 	PostOAuthCallback(c *gin.Context)
 }
@@ -55,14 +53,6 @@ func (m *managementTokenRequester) RequestKimiToken(c *gin.Context) {
 	m.handler.RequestKimiToken(c)
 }
 
-func (m *managementTokenRequester) RequestIFlowToken(c *gin.Context) {
-	m.handler.RequestIFlowToken(c)
-}
-
-func (m *managementTokenRequester) RequestIFlowCookieToken(c *gin.Context) {
-	m.handler.RequestIFlowCookieToken(c)
-}
-
 func (m *managementTokenRequester) GetAuthStatus(c *gin.Context) {
 	m.handler.GetAuthStatus(c)
 }