refactor: Extract coverart library to separate repository

- Move Bento4 library and JNI wrapper to metrolist-coverart-lib repository
- Replace embedded code with git submodule reference
- This reduces main repository size by ~77,000 lines
- Library can now be independently versioned and updated

Submodule: https://github.com/MetrolistGroup/metrolist-coverart-lib

Author: mostafaalagamy

.gitmodules

@@ -1,3 +1,6 @@
 [submodule "metroproto"]
 	path = metroproto
 	url = https://github.com/MetrolistGroup/metroproto
+[submodule "app/src/main/cpp/coverart"]
+	path = app/src/main/cpp/coverart
+	url = https://github.com/MetrolistGroup/metrolist-coverart-lib.git