Fix file watcher to process moved files from temporary locations

[Acren]

Problem

The file watcher was not detecting files created by editors that use a "create temp file then move to final location" pattern.
This caused newly created files to be missed by the auto-indexing system.

Root cause: File watcher only checked event.src_path (temporary file) but ignored event.dest_path (final file location) for move events.

e.g.

1. User creates file my_file.py
2. Editor saves as my_file.py.tmp.2644.1754398445351 or similar
3. Editor renames my_file.py.tmp.2644.1754398445351 -> my_file.py
4. Because only the source path is checked, the file watcher ignores the file and discards the event

Solution

• Enhanced move event handling: Check dest_path for moved events to detect final file location
• Refactored path checking: Extract filtering logic to reusable _should_process_path() method

Testing

• Created test files that trigger the temp-file-move pattern
• Verified move events now properly detect destination files with supported extensions
• Confirmed temporary files are still filtered out correctly

Files Changed

• src/code_index_mcp/services/file_watcher_service.py: Enhanced move event handling