Rename product to dockmv (container, image, module, env vars)

Container/image/service name, Go module path, CLI binary name, and
DOCKER_MIGRATE_* env vars still used the old working name; the project
is branded DockMV everywhere else (README, logo, Gitea repo).

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

web/src/Sidebar.tsx

@@ -425,7 +425,7 @@ function ConnectionDialog({
 
         {c.auth === 'agent' && (
           <div className="small muted">
-            Uses the agent at <span className="mono">$SSH_AUTH_SOCK</span> of the process running docker-migrate.
+            Uses the agent at <span className="mono">$SSH_AUTH_SOCK</span> of the process running dockmv.
           </div>
         )}
 
@@ -452,7 +452,7 @@ function ConnectionDialog({
           </Notice>
         ) : (
           <div className="small faint">
-            Credentials stay in memory and are lost when docker-migrate restarts.
+            Credentials stay in memory and are lost when dockmv restarts.
           </div>
         )}
       </div>