fix: Add 'waitlist' status to sign-in redirect logic

CRITICAL FIX: Resolves infinite redirect loop on sign-in for waitlist users.

Root Cause:
- signinUser() function was missing "waitlist" in status check (line 289-295)
- Users with "waitlist" status would get redirectTo = "/home" (default)
- Middleware would then redirect them to "/applicant/waiting"
- SignInForm would redirect to "/home" again
- INFINITE REDIRECT LOOP

The Fix:
- Added "waitlist" to applicant status conditions in signinUser()
- Now correctly redirects waitlist users to "/applicant/waiting"
- Matches middleware logic for consistent redirect behavior

This completes the waitlist status handling across:
1. ✅ Middleware (fixed in previous commit)
2. ✅ Sign-in action (fixed in this commit)
3. ✅ TypeScript types (fixed in previous commit)

Impact:
- Fixes ERR_TOO_MANY_REDIRECTS for users signing in with waitlist status
- Ensures smooth sign-in experience for all applicant statuses
- No more redirect loops between /home and /applicant/waiting

🤖 Generated with [Claude Code](https://claude.com/claude-code)

Co-Authored-By: Claude <noreply@anthropic.com>

Author: Zeff01

apps/codebility/app/auth/actions.ts

@@ -290,7 +290,8 @@ export const signinUser = async (email: string, password: string) => {
       userProfile.application_status === "applying" ||
       userProfile.application_status === "pending" ||
       userProfile.application_status === "testing" ||
-      userProfile.application_status === "onboarding"
+      userProfile.application_status === "onboarding" ||
+      userProfile.application_status === "waitlist"
     ) {
       redirectTo = "/applicant/waiting";
     } else if (