feat(domain): Add extract_meta() and crop() to VectorDocument

- extract_meta(): Extract basic metadata (SVG format, native dimensions)
- crop(): Render-based crop on rasterized output
- Completes VectorDocument feature parity with app/

Refs: Migration Step 1.3

DEVNOTE/Feature-Comparison.md

@@ -139,10 +139,10 @@
 - [x] `handle()` getter - Bereits vorhanden! ✅
 
 ### Schritt 1.3: VectorDocument (45 Min)
-- [ ] `dimensions()` implementieren
-- [ ] `handle()` getter hinzufügen
-- [ ] `extract_meta()` implementieren
-- [ ] `crop()` implementieren (render-based, neu!)
+- [x] `dimensions()` - Bereits vorhanden ✅
+- [x] `handle()` getter - Bereits vorhanden ✅
+- [x] `extract_meta()` implementieren ✅
+- [x] `crop()` implementieren (render-based) ✅
 
 ### Schritt 1.4: PortableDocument (45 Min)
 - [ ] `dimensions()` implementieren