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/recover.ts

@@ -94,7 +94,7 @@ router.post("/", recoverLimiter, async (req: Request, res: Response) => {
 
     res.json({ status: "recovery_sent", message: "If an account exists for this email, a verification code has been sent." });
   } catch (err: unknown) {
-    const reqId = (req as any).requestId || "unknown";
+    const reqId = req.requestId || "unknown";
     logger.error({ err, requestId: reqId }, "Unhandled error in POST /recover");
     res.status(500).json({ error: "Internal server error" });
   }
@@ -210,7 +210,7 @@ router.post("/verify", recoverLimiter, async (req: Request, res: Response) => {
         break;
     }
   } catch (err: unknown) {
-    const reqId = (req as any).requestId || "unknown";
+    const reqId = req.requestId || "unknown";
     logger.error({ err, requestId: reqId }, "Unhandled error in POST /recover/verify");
     res.status(500).json({ error: "Internal server error" });
   }