dedup: modulo audio fingerprinting via fpcalc + cache SQLite

Nuovo modulo core.dedup per rilevare brani audio duplicati usando
Chromaprint (fpcalc): scan cartella (opzionalmente ricorsivo),
fingerprint acustico via fpcalc -json, cache SQLite in
_get_config_dir()/dedup_cache.db per non ricalcolare al re-scan,
raggruppamento per fingerprint identico + ordering per bitrate DESC.
move_to_trash() usa send2trash (reversibile via Finder/Explorer).

- core/paths.py: find_fpcalc() con fallback dev su project bundle_bin
- core/dedup.py: scan_folder, compute_fingerprint, move_to_trash
- tests/test_dedup.py: 9 unit test (mock fpcalc + send2trash)
- requirements.txt: send2trash>=1.8.0
- build_macos.py: download fpcalc universal binary da GitHub releases
- build_windows.py: download fpcalc.exe da GitHub releases

requirements.txt

@@ -11,6 +11,7 @@ pythonnet==3.0.5 ; sys_platform == "win32"
 clr-loader==0.2.7.post0 ; sys_platform == "win32"
 curl_cffi>=0.9.0
 beautifulsoup4>=4.12.0
+send2trash>=1.8.0
 
 # --- dev only ---
 pytest>=8.0.0