feat(security): enhance email validation and sanitization

- Updates `isValidEmail` to strictly reject double quotes and backticks while allowing apostrophes.
- Applies `sanitizeInput` to email fields in Contact form payload (Defense in Depth).
- Adds tests for email validation edge cases.
- Updates Sentinel journal.

Co-authored-by: ragusa-it <196988693+ragusa-it@users.noreply.github.com>

src/pages/Contact.tsx

@@ -93,7 +93,7 @@ export function Contact() {
     try {
       const templateParams = {
         name: sanitizeInput(formData.name),
-        email: formData.email, // Email doesn't typically need HTML sanitization if validated by regex, but good practice to handle it if used in HTML context.
+        email: sanitizeInput(formData.email),
         title: sanitizeInput(formData.subject),
         message: sanitizeInput(formData.message),
         reply_to: formData.email,