feat: Phase 2 — RAG integration in Requirements + DSFA Draft

Add legal context enrichment from Qdrant vector corpus to the two
highest-priority modules (Requirements AI assistant and DSFA drafting
engine).

Go SDK:
- Add SearchCollection() with collection override + whitelist validation
- Refactor Search() to delegate to shared searchInternal()

Python backend:
- New ComplianceRAGClient proxying POST /sdk/v1/rag/search (error-tolerant)
- AI assistant: enrich interpret_requirement() and suggest_controls() with RAG
- Requirements API: add ?include_legal_context=true query parameter

Admin (Next.js):
- Extract shared queryRAG() utility from chat route
- Inject RAG legal context into v1 and v2 draft pipelines

Tests for all three layers (Go, Python, TypeScript shared utility).

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

admin-compliance/lib/sdk/drafting-engine/rag-query.ts

@@ -0,0 +1,40 @@
+/**
+ * Shared RAG query utility for the Drafting Engine.
+ *
+ * Queries the DSFA RAG corpus via klausur-service for relevant legal context.
+ * Used by both chat and draft routes.
+ */
+
+const KLAUSUR_SERVICE_URL = process.env.KLAUSUR_SERVICE_URL || 'http://klausur-service:8086'
+
+/**
+ * Query the RAG corpus for relevant legal documents.
+ *
+ * @param query - The search query (e.g. "DSFA Art. 35 DSGVO")
+ * @param topK - Number of results to return (default: 3)
+ * @returns Formatted string of legal context, or empty string on error
+ */
+export async function queryRAG(query: string, topK = 3): Promise<string> {
+  try {
+    const url = `${KLAUSUR_SERVICE_URL}/api/v1/dsfa-rag/search?query=${encodeURIComponent(query)}&top_k=${topK}`
+    const res = await fetch(url, {
+      headers: { 'Content-Type': 'application/json' },
+      signal: AbortSignal.timeout(10000),
+    })
+
+    if (!res.ok) return ''
+
+    const data = await res.json()
+    if (data.results?.length > 0) {
+      return data.results
+        .map(
+          (r: { source_name?: string; source_code?: string; content?: string }, i: number) =>
+            `[Quelle ${i + 1}: ${r.source_name || r.source_code || 'Unbekannt'}]\n${r.content || ''}`
+        )
+        .join('\n\n---\n\n')
+    }
+    return ''
+  } catch {
+    return ''
+  }
+}