fix: remove unnecessary 'as any' casts and add proper types to templates

- Replace (req as any).requestId with req.requestId in index.ts, recover.ts, email-change.ts
- Replace (err as any).status with proper Record<string, unknown> narrowing in error handler
- Add InvoiceData, ReceiptData, ContactInfo, InvoiceItem, ReceiptItem interfaces to templates.ts
- Replace all 'any' params in template functions with proper types
- Add type-safety regression tests (grep-based)
- 818 tests pass, tsc --noEmit: 0 errors

src/__tests__/templates.test.ts

@@ -1,10 +1,10 @@
 import { describe, it, expect } from "vitest";
-import { renderTemplate, templates } from "../services/templates.js";
+import { renderTemplate, templates, TemplateData } from "../services/templates.js";
 
 // Access esc via rendering — test that HTML entities are escaped in output
 describe("Template rendering", () => {
   it("throws for unknown template", () => {
-    expect(() => renderTemplate("nonexistent", {})).toThrow("not found");
+    expect(() => renderTemplate("nonexistent", {} as TemplateData)).toThrow("not found");
   });
 
   it("invoice renders with correct totals", () => {

src/__tests__/type-safety.test.ts

@@ -0,0 +1,31 @@
+import { describe, it, expect } from "vitest";
+import { execSync } from "child_process";
+import path from "path";
+
+describe("Type safety", () => {
+  const srcDir = path.resolve(__dirname, "..");
+
+  it("should not use (req as any).requestId in production code — Express.Request is already augmented", () => {
+    const result = execSync(
+      `grep -r "(req as any)\\.requestId" --include="*.ts" --exclude-dir=__tests__ "${srcDir}" || true`,
+      { encoding: "utf-8" }
+    );
+    expect(result.trim()).toBe("");
+  });
+
+  it("should not use (err as any) — use proper type narrowing instead", () => {
+    const result = execSync(
+      `grep -r "(err as any)" --include="*.ts" "${srcDir}" --exclude-dir=__tests__ || true`,
+      { encoding: "utf-8" }
+    );
+    expect(result.trim()).toBe("");
+  });
+
+  it("should not use any types in templates.ts function parameters", () => {
+    const result = execSync(
+      `grep -E "\\(d: any\\)|\\(data: any\\)|\\(item: any\\)" "${srcDir}/services/templates.ts" || true`,
+      { encoding: "utf-8" }
+    );
+    expect(result.trim()).toBe("");
+  });
+});