feat: add products/cases pages and lead-capture form block

- types: Product/CaseStudy page types, CaseStudyBlockValue, FormBlockValue
- services: product.service.ts, case.service.ts
- app/products, app/cases: list + detail pages
- blocks: CaseStudyCard, LeadForm (submits to /api/v1/custom/leads/)
- Header nav: add 产品/案例 links

blocks/BlockRenderer.tsx

@@ -5,10 +5,12 @@ import FeatureGrid from "./feature-grid/FeatureGrid";
 import FAQ from "./faq/FAQ";
 import CTA from "./cta/CTA";
 import LogoCloud from "./logo-cloud/LogoCloud";
+import CaseStudyCard from "./case-study/CaseStudyCard";
+import LeadForm from "./form/LeadForm";
 import type { StreamFieldBlock } from "@/types/wagtail";
 
 /**
- * StreamField type → 组件映射表。
+ * StreamField 类型 → 组件映射表。
  * 必须与后端 apps/core/blocks.py 的 COMMON_BLOCKS 保持一致，
  * 否则新增/重命名 Block 时前后端会出现字段不对齐问题
  * （详见 documents/设计方案分析与完善版.md §2.6）。
@@ -21,6 +23,8 @@ const components: Record<string, ComponentType<{ value: any }>> = {
   faq: FAQ,
   cta: CTA,
   logo_cloud: LogoCloud,
+  case_study: CaseStudyCard,
+  form: LeadForm,
 };
 
 export function BlockRenderer({ blocks }: { blocks: StreamFieldBlock[] }) {