Fix sub-session tab switching: reset step state on sessionId change

Step components (Deskew, Dewarp, Crop, Orientation) had local state
guards that prevented reloading when sessionId changed via sub-session
tab clicks. Added useEffect reset hooks that clear all local state
when sessionId changes, allowing the component to properly reload
the new session's data.

Also renamed "Box N" to "Seite N" in BoxSessionTabs per user feedback.

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

admin-lehrer/components/ocr-pipeline/BoxSessionTabs.tsx

@@ -59,7 +59,7 @@ export function BoxSessionTabs({ parentSessionId, subSessions, activeSessionId,
             title={sub.name}
           >
             <span className="mr-1">{icon}</span>
-            Box {sub.box_index + 1}
+            Seite {sub.box_index + 1}
           </button>
         )
       })}