fix(tracks): removing a track writes a track_remove audit row (#6294)

RemoveTrack took the admin's id and dropped it, so a merge left an
audit trail and the more destructive removal did not. It now reads the
track's title, artist, album and file path before the delete and writes
them, with whether the album and artist went too, under the new
track_remove action.

The audit action groups lose their plan-era U1/U2/U3 headings.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

internal/audit/audit.go

@@ -20,14 +20,13 @@ import (
 	"git.fabledsword.com/bvandeusen/minstrel/internal/db/dbq"
 )
 
-// Action is the discriminator stored in audit_log.action. New values
-// added in U2/U3 + future tasks; declare them here so callers don't
-// stringly-type and so a future audit-search UI has a single source
-// of truth for the vocabulary.
+// Action is the discriminator stored in audit_log.action. Every value is
+// declared here, so callers never stringly-type an action and the vocabulary
+// has one source.
 type Action string
 
 const (
-	// U1
+	// Accounts and invites.
 	ActionRegister     Action = "register"
 	ActionPromoteAdmin Action = "promote_admin"
 	ActionDemoteAdmin  Action = "demote_admin"
@@ -35,15 +34,13 @@ const (
 	ActionInviteRedeem Action = "invite_redeem"
 	ActionInviteRevoke Action = "invite_revoke"
 
-	// U2 (declared early; callers in U1 don't use them yet, but
-	// having them here means U2's diff is purely additive on the
-	// caller side, not also touching this file).
+	// Admin user management.
 	ActionCreateUserAdmin    Action = "create_user_admin"
 	ActionDeleteUser         Action = "delete_user"
 	ActionPasswordResetAdmin Action = "password_reset_admin"
 	ActionAutoApproveToggle  Action = "auto_approve_toggle"
 
-	// U3
+	// Credentials.
 	ActionPasswordChangeSelf   Action = "password_change_self"
 	ActionTokenRegenerate      Action = "token_regenerate"
 	ActionForgotPasswordInit   Action = "forgot_password_initiated"
@@ -65,6 +62,12 @@ const (
 	ActionDuplicateDismiss   Action = "duplicate_dismiss"
 	ActionDuplicateWrongFile Action = "duplicate_wrong_file"
 
+	// An admin removing a track: its file and row are deleted, with every
+	// like, play and playlist entry that hung off the row. The metadata names
+	// the track and its file, so the log can say what went after the row is
+	// gone.
+	ActionTrackRemove Action = "track_remove"
+
 	// Subsonic password: generated in Settings for t/s-only clients.
 	ActionSubsonicPasswordSet   Action = "subsonic_password_set"
 	ActionSubsonicPasswordClear Action = "subsonic_password_clear"