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/routes/templates.ts

@@ -1,7 +1,7 @@
 import { Router, Request, Response } from "express";
 import { renderPdf } from "../services/browser.js";
 import logger from "../services/logger.js";
-import { templates, renderTemplate } from "../services/templates.js";
+import { templates, renderTemplate, TemplateData } from "../services/templates.js";
 import { sanitizeFilename } from "../utils/sanitize.js";
 import { validatePdfOptions } from "../utils/pdf-options.js";
 
@@ -165,7 +165,7 @@ templatesRouter.post("/:id/render", async (req: Request, res: Response) => {
     }
     const sanitizedPdf = { format: "A4" as const, ...validation.sanitized };
 
-    const html = renderTemplate(id, data);
+    const html = renderTemplate(id, data as TemplateData);
     const { pdf, durationMs } = await renderPdf(html, sanitizedPdf);
 
     const filename = sanitizeFilename(data._filename || `${id}.pdf`);