Refresh scanner details of findings that are seen again

A rescan only touched the timestamp of findings it had seen before, so a
newly published fix version, a changed severity and the package source
never reached existing rows. The repository now updates those fields
while keeping first_seen and the status the user set.

Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>

backend/crates/domain/src/ports.rs

@@ -140,9 +140,11 @@ pub trait FindingRepository: Send + Sync {
     /// Open and acknowledged findings of one target.
     async fn active_by_target(&self, target: &str) -> Result<Vec<Finding>, DomainError>;
     async fn insert(&self, finding: &Finding) -> Result<(), DomainError>;
-    async fn touch(
+    /// Mark findings as seen again and update the details the scanner may have changed
+    /// (severity, fix version, title, source).
+    async fn refresh(
         &self,
-        ids: &[Uuid],
+        updates: &[(Uuid, RawFinding)],
         last_seen: chrono::DateTime<chrono::Utc>,
     ) -> Result<(), DomainError>;
     async fn set_status(&self, id: Uuid, status: FindingStatus) -> Result<(), DomainError>;