feat(auth): transition from email to phone-based OTP authentication

- Replace Email+Password login with Phone+OTP flow
- Remove RegisterCubit and registration screens (email verification)
- Remove ResetPasswordCubit and reset password screens
- Add phone normalization and international dial code support
- Update LoginCubit with sendCode/resend cooldown logic
- Add new widgets: phone prefix selector, confirm sheet
- Update all auth API endpoints: /otp/send, /phone-session
- Update form inputs: Email -> Phone with E.164 validation
- Update tests for new auth flow

apps/lib/features/auth/ui/widgets/auth_page_scaffold.dart

@@ -9,12 +9,14 @@ class AuthPageScaffold extends StatelessWidget {
     this.footer,
     this.mainContentKey,
     this.footerKey,
+    this.resizeOnKeyboard = true,
   });
 
   final Widget mainContent;
   final Widget? footer;
   final Key? mainContentKey;
   final Key? footerKey;
+  final bool resizeOnKeyboard;
 
   @override
   Widget build(BuildContext context) {
@@ -22,6 +24,7 @@ class AuthPageScaffold extends StatelessWidget {
 
     return Scaffold(
       backgroundColor: AppColors.authBackgroundBottom,
+      resizeToAvoidBottomInset: resizeOnKeyboard,
       body: DecoratedBox(
         decoration: const BoxDecoration(
           gradient: LinearGradient(
@@ -37,8 +40,33 @@ class AuthPageScaffold extends StatelessWidget {
           children: [
             const _AuthBackgroundOrbs(),
             SafeArea(
+              maintainBottomViewPadding: !resizeOnKeyboard,
               child: LayoutBuilder(
                 builder: (context, constraints) {
+                  if (!resizeOnKeyboard) {
+                    return Padding(
+                      padding: const EdgeInsets.symmetric(
+                        horizontal: AppSpacing.lg,
+                      ),
+                      child: Center(
+                        child: Column(
+                          mainAxisSize: MainAxisSize.min,
+                          crossAxisAlignment: CrossAxisAlignment.center,
+                          children: [
+                            KeyedSubtree(
+                              key: mainContentKey,
+                              child: mainContent,
+                            ),
+                            if (footer != null) ...[
+                              SizedBox(height: AppSpacing.md),
+                              KeyedSubtree(key: footerKey, child: footer!),
+                            ],
+                          ],
+                        ),
+                      ),
+                    );
+                  }
+
                   return SingleChildScrollView(
                     keyboardDismissBehavior:
                         ScrollViewKeyboardDismissBehavior.onDrag,