refactor: section the config and make prompts a module

backend/app/domain/matching.py

@@ -12,7 +12,11 @@ _SUFFIX_PATTERN = re.compile(r"(?:\s*(?:\([^)]*\)|\[[^]]*\]))+\s*$")
 
 @dataclass(frozen=True)
 class MatchVerdict:
-    """Explain whether a Spotify track safely matches a proposed candidate."""
+    """Match decision plus the two signals it was derived from.
+
+    A rejection is attributable: either title_similarity fell below the
+    caller's threshold, or is_artist_match is false, or both.
+    """
 
     is_match: bool
     title_similarity: float