Fix RemoveUnusedImports command wiring

[amanthatdoescares]

Problem

The RemoveUnusedImports feature only considered imports at the top level of files, missing imports inside #if conditional compilation blocks. This led to:

• False negatives: Unused imports inside #if blocks weren't detected
• Incomplete cleanup: Projects with platform-specific or feature-flagged imports wouldn't get fully cleaned up

Solution

Implement recursive syntax tree traversal to find ALL imports throughout the entire file structure, including those inside conditional compilation blocks.
Fixes: #2335

Now properly handles all imports including those inside #if blocks while keeping platform-specific imports safe.