Fundament: Audit mit IP/User-Agent, Mail-Absender je Mandant

- Migration audit_request_context: ip_address, user_agent an audit_logs (Spec §26)
- writeAuditLog/writePlatformAudit erfassen IP (X-Forwarded-For) und User-Agent
  aus dem Request; außerhalb eines Requests (Worker/Skripte) null
- Audit-Viewer liest die neuen Spalten statt Heuristik aus before/after
- deliverMail nutzt Anzeigename und Reply-To aus TenantSettings (Spec §33.2);
  Absenderadresse bleibt Plattform-Domain (SPF/DKIM), Header-Injection bereinigt

Gate: tsc, lint, build, 24/24 Tests grün.

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

src/server/services/audit/viewer.ts

@@ -100,19 +100,6 @@ export function diffAudit(before: unknown, after: unknown): DiffRow[] {
   });
 }
 
-/** Extract request metadata if a writer stored it (writeAuditLog does not capture it yet). */
-function requestMeta(...sources: unknown[]): { ip: string | null; userAgent: string | null } {
-  for (const s of sources) {
-    if (s && typeof s === "object") {
-      const o = s as Record<string, unknown>;
-      const ip = typeof o.ip === "string" ? o.ip : null;
-      const userAgent = typeof o.userAgent === "string" ? o.userAgent : null;
-      if (ip || userAgent) return { ip, userAgent };
-    }
-  }
-  return { ip: null, userAgent: null };
-}
-
 export async function getAuditEntry(ctx: ServiceCtx, id: unknown) {
   assertCan(ctx, "audit:read");
   const entryId = z.string().min(1).max(64).parse(id);
@@ -123,6 +110,8 @@ export async function getAuditEntry(ctx: ServiceCtx, id: unknown) {
     ...row,
     actorName: actor?.name ?? null,
     diff: diffAudit(row.before ?? undefined, row.after ?? undefined),
-    ...requestMeta(row.after, row.before),
+    // captured by writeAuditLog from the request (spec §26); null for worker/script writes
+    ip: row.ipAddress,
+    userAgent: row.userAgent,
   };
 }