feat(worker): add post-merge verification gate for list merges

Per-list optional VerifyCommand (list_config.verify_command) runs via
VerifyCommandRunner in the list's working dir right after a successful
merge/continue-merge, before the task is allowed to reach Done. A
non-zero exit or timeout leaves the merge in place but keeps the task
out of Done and reports StatusVerifyFailed with an output excerpt
through MergeResultDto/review_task; no command configured behaves
exactly as before. Merges against the same repo are now serialized
per working dir so a running verify can't be interrupted by a second
merge landing mid-build. Adds the field to the List Settings modal
(en/de localized) and covers success/failure/timeout in
TaskMergeServiceTests + VerifyCommandRunnerTests.

src/ClaudeDo.Data/Configuration/ListConfigEntityConfiguration.cs

@@ -17,5 +17,6 @@ public class ListConfigEntityConfiguration : IEntityTypeConfiguration<ListConfig
         builder.Property(c => c.AgentPath).HasColumnName("agent_path");
         builder.Property(c => c.MaxTurns).HasColumnName("max_turns");
         builder.Property(c => c.SessionSkills).HasColumnName("session_skills");
+        builder.Property(c => c.VerifyCommand).HasColumnName("verify_command");
     }
 }