Add contact actions and migrate contact form to Astro actions

Implement send_otp and send_msg handlers with server-side validation,
captcha verification, OTP generation/verification, rate limiting,
session-backed multi-step flow, and SMS gateway integration.

Replace broken contact endpoint and types with Astro server actions;
delete endpoints/contact.ts, types/ContactForm.ts and
src/components/ContactForm.astro. Update pages/contact.astro to use
astro:actions and improve captcha handling (listen for solve and set
hidden input). Adjust OTP timing (step 60s → 300s, VALID_PAST_OTP_STEPS
5 → 1). Add validator, @types/validator, Prettier and
prettier-plugin-astro; include .prettierrc.mjs in tsconfig include.

Add Prettier config for Astro

package.json

@@ -31,9 +31,13 @@
     "htmx.org": "^2.0.8",
     "iconify-icon": "^3.0.2",
     "otplib": "^12.0.1",
-    "typescript": "^5.9.3"
+    "typescript": "^5.9.3",
+    "validator": "^13.15.26"
   },
   "devDependencies": {
-    "@types/bun": "^1.3.5"
+    "@types/bun": "^1.3.5",
+    "@types/validator": "^13.15.10",
+    "prettier": "^3.8.1",
+    "prettier-plugin-astro": "^0.14.1"
   }
 }