Phase 5: Reorganize headers and add missing imports

Changes:
- Add BNCConfig.h import to BranchSDK.h
- Add BranchConstants.h import to BranchSDK.h
- Update BranchConfigurationController.m to use Private/ path for header import

Purpose:
- Improve header organization
- Make private headers explicit via Private/ path
- Add missing public header imports
- Better separation of public vs private APIs

Build Status: ✅ Successful

Author: wpinho-branch

Sources/BranchSDK/BranchConfigurationController.m

@@ -5,7 +5,7 @@
 //  Created by Nidhi Dixit on 6/2/25.
 //
 
-#import "BranchConfigurationController.h"
+#import "Private/BranchConfigurationController.h"
 #import "BNCPreferenceHelper.h"
 #import "BranchLogger.h"
 #import "BranchConstants.h"

Sources/BranchSDK/Public/BranchSDK.h

@@ -19,6 +19,7 @@ FOUNDATION_EXPORT const unsigned char BranchSDKVersionString[];
 
 #import "BranchScene.h"
 #import "BranchDelegate.h"
+#import "BNCConfig.h"
 
 #import "BranchEvent.h"
 #import "BranchLinkProperties.h"
@@ -58,3 +59,5 @@ FOUNDATION_EXPORT const unsigned char BranchSDKVersionString[];
 
 // BNCLinkCache.h uses BNCLinkData.h
 #import "BNCLinkData.h"
+
+#import "BranchConstants.h"