feat(dsms): Stufe 2+3 — Evidence/TechFile → DSMS + Version Chains + Audit Timeline

Stufe 2A: Evidence Upload → automatische DSMS-Archivierung
- Nach SHA-256 Hash → archive_to_dsms(), CID im Audit-Trail
- Evidence mit CID wird automatisch zu E2 (hash-verifiziert) hochgestuft

Stufe 2B: IACE Tech-File Export → DSMS
- PDF/Excel/DOCX/Markdown Exporte werden nach DSMS archiviert
- archiveTechFile() Helper fuer alle 4 Formate

Stufe 3A: DSMS Gateway — parent_cid + History Endpoint
- parent_cid + tenant_id Felder in DocumentMetadata
- GET /documents/{cid}/history — folgt parent_cid-Chain (max 50 deep)

Stufe 3C: Audit Timeline UI
- Neue Seite /sdk/audit-timeline
- Vertikale Timeline mit farbigen Action-Dots
- Filter: Alle, Nachweis, DSMS-Archiv, Control, Dokument, DSFA, VVT, TOM
- CID-Badges fuer DSMS-archivierte Eintraege

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

dsms-gateway/routers/documents.py

@@ -254,3 +254,34 @@ async def archive_legal_document(
         "archived_at": datetime.utcnow().isoformat(),
         "verification_url": f"{IPFS_GATEWAY_URL}/ipfs/{cid}"
     }
+
+
+@router.get("/documents/{cid}/history")
+async def get_document_history(cid: str):
+    """Follow the parent_cid chain to reconstruct version history."""
+    history = []
+    current_cid = cid
+    max_depth = 50  # prevent infinite loops
+
+    for _ in range(max_depth):
+        try:
+            raw = await ipfs_cat(current_cid)
+            package = json.loads(raw)
+            metadata = package.get("metadata", {})
+            history.append({
+                "cid": current_cid,
+                "version": metadata.get("version"),
+                "document_type": metadata.get("document_type"),
+                "document_id": metadata.get("document_id"),
+                "parent_cid": metadata.get("parent_cid"),
+                "created_at": metadata.get("created_at"),
+                "checksum": metadata.get("checksum"),
+            })
+            parent = metadata.get("parent_cid")
+            if not parent:
+                break
+            current_cid = parent
+        except Exception:
+            break
+
+    return {"cid": cid, "history": history, "depth": len(history)}