feat: expose generic tenant-safe ER candidate API

app/api/0pt/er/candidates/route.ts

@@ -0,0 +1,17 @@
+import { NextRequest, NextResponse } from "next/server";
+
+import { parseErCandidateRequest } from "@/src/er/request-validation";
+import { assertTenantMatchesVerified } from "@/src/http/tenant-guard";
+import { siaxErrorResponse } from "@/src/http/siax-error-response";
+import { entityResolutionService } from "@/src/services/entity-resolution";
+
+export async function POST(request: NextRequest) {
+  try {
+    const input = parseErCandidateRequest(await request.json());
+    const guard = assertTenantMatchesVerified(request, input.tenant_id);
+    if (guard) return guard;
+    return NextResponse.json(entityResolutionService.generateCandidates(input));
+  } catch (error: unknown) {
+    return siaxErrorResponse(error);
+  }
+}