feat(auth): ChangePasswordException sealed class with typed failure reasons

app/src/main/java/app/closer/domain/repository/ChangePasswordException.kt

@@ -0,0 +1,23 @@
+package app.closer.domain.repository
+
+/**
+ * Typed reasons a signed-in password change can fail, mapped from Firebase specifics at the auth
+ * data-source boundary. Using these instead of matching on Firebase's human-readable error strings keeps
+ * detection robust across SDK/locale changes; the UI layer owns the user-facing copy per type.
+ */
+sealed class ChangePasswordException(message: String) : Exception(message) {
+    /** The current password entered for re-authentication was wrong. */
+    class WrongCurrentPassword : ChangePasswordException("Current password incorrect")
+
+    /** The new password doesn't meet Firebase's strength requirement. */
+    class WeakNewPassword : ChangePasswordException("New password too weak")
+
+    /** Firebase is throttling after too many attempts — back off and retry later. */
+    class TooManyAttempts : ChangePasswordException("Too many attempts")
+
+    /** The session is too old; the user must sign in again before changing the password. */
+    class ReauthRequired : ChangePasswordException("Recent sign-in required")
+
+    /** This account has no password to change (e.g. Google sign-in only). */
+    class NoPassword : ChangePasswordException("Account has no password")
+}