feat(auth): add email sign-in page

- Implemented email link sign-in flow
- Added email form with validation
- Navigates to code verification page

Author: fulleni

lib/authentication/view/request_code_page.dart

@@ -0,0 +1,222 @@
+//
+// ignore_for_file: lines_longer_than_80_chars
+
+import 'package:flutter/material.dart';
+import 'package:flutter_bloc/flutter_bloc.dart';
+import 'package:go_router/go_router.dart';
+import 'package:ht_main/authentication/bloc/authentication_bloc.dart';
+import 'package:ht_main/l10n/l10n.dart';
+import 'package:ht_main/router/routes.dart';
+import 'package:ht_main/shared/constants/app_spacing.dart';
+
+/// {@template email_sign_in_page}
+/// Page for initiating the email link sign-in process.
+/// Explains the passwordless flow and collects the user's email.
+/// {@endtemplate}
+class EmailSignInPage extends StatelessWidget {
+  /// {@macro email_sign_in_page}
+  const EmailSignInPage({
+    required this.isLinkingContext, // Accept the flag
+    super.key,
+  });
+
+  /// Whether this page is being shown in the account linking context.
+  final bool isLinkingContext;
+
+  @override
+  Widget build(BuildContext context) {
+    // Assuming AuthenticationBloc is provided by the parent route (AuthenticationPage)
+    // If not, it needs to be provided here or higher up.
+    // Pass the flag down to the view.
+    return _EmailSignInView(isLinkingContext: isLinkingContext);
+  }
+}
+
+class _EmailSignInView extends StatelessWidget {
+  // Accept the flag from the parent page.
+  const _EmailSignInView({required this.isLinkingContext});
+
+  final bool isLinkingContext;
+
+  @override
+  Widget build(BuildContext context) {
+    final l10n = context.l10n;
+    final colorScheme = Theme.of(context).colorScheme;
+
+    return Scaffold(
+      appBar: AppBar(
+        title: Text(l10n.emailSignInPageTitle),
+        // Add a custom leading back button to control navigation based on context.
+        leading: IconButton(
+          icon: const Icon(Icons.arrow_back),
+          tooltip:
+              MaterialLocalizations.of(
+                context,
+              ).backButtonTooltip, // Accessibility
+          onPressed: () {
+            // Navigate back differently based on the context.
+            if (isLinkingContext) {
+              // If linking, go back to Auth page preserving the linking query param.
+              context.goNamed(
+                Routes.authenticationName,
+                queryParameters: {'context': 'linking'},
+              );
+            } else {
+              // If normal sign-in, just go back to the Auth page.
+              context.goNamed(Routes.authenticationName);
+            }
+          },
+        ),
+      ),
+      body: SafeArea(
+        child: BlocConsumer<AuthenticationBloc, AuthenticationState>(
+          listener: (context, state) {
+            if (state is AuthenticationFailure) {
+              ScaffoldMessenger.of(context)
+                ..hideCurrentSnackBar()
+                ..showSnackBar(
+                  SnackBar(
+                    content: Text(state.errorMessage),
+                    backgroundColor: colorScheme.error,
+                  ),
+                );
+            } else if (state is AuthenticationCodeSentSuccess) {
+              // Navigate to the code verification page on success, passing the email
+              context.goNamed(
+                Routes.verifyCodeName,
+                pathParameters: {'email': state.email},
+              );
+            }
+          },
+          // BuildWhen prevents unnecessary rebuilds if only listening
+          buildWhen:
+              (previous, current) =>
+                  current is AuthenticationInitial ||
+                  current is AuthenticationRequestCodeLoading ||
+                  current
+                      is AuthenticationFailure, // Rebuild on failure to re-enable form
+          builder: (context, state) {
+            final isLoading = state is AuthenticationRequestCodeLoading;
+
+            return Padding(
+              padding: const EdgeInsets.all(AppSpacing.paddingLarge),
+              child: Center(
+                child: SingleChildScrollView(
+                  child: Column(
+                    mainAxisAlignment: MainAxisAlignment.center,
+                    crossAxisAlignment: CrossAxisAlignment.stretch,
+                    children: [
+                      // --- Hardcoded Icon ---
+                      Padding(
+                        padding: const EdgeInsets.only(
+                          bottom: AppSpacing.xl,
+                        ), // Spacing below icon
+                        child: Icon(
+                          Icons.email_outlined, // Hardcoded icon
+                          size:
+                              (Theme.of(context).iconTheme.size ??
+                                  AppSpacing.xl) *
+                              3.0,
+                          color: Theme.of(context).colorScheme.primary,
+                        ),
+                      ),
+                      const SizedBox(
+                        height: AppSpacing.lg,
+                      ), // Space between icon and text
+                      // --- Explanation Text ---
+                      Text(
+                        l10n.emailSignInExplanation,
+                        style: Theme.of(context).textTheme.bodyLarge,
+                        textAlign: TextAlign.center,
+                      ),
+                      const SizedBox(height: AppSpacing.xxl),
+                      _EmailLinkForm(isLoading: isLoading),
+                    ],
+                  ),
+                ),
+              ),
+            );
+          },
+        ),
+      ),
+    );
+  }
+}
+
+/// --- Reusable Email Form Widget --- ///
+
+class _EmailLinkForm extends StatefulWidget {
+  const _EmailLinkForm({required this.isLoading});
+
+  final bool isLoading;
+
+  @override
+  State<_EmailLinkForm> createState() => _EmailLinkFormState();
+}
+
+class _EmailLinkFormState extends State<_EmailLinkForm> {
+  final _emailController = TextEditingController();
+  final _formKey = GlobalKey<FormState>();
+
+  @override
+  void dispose() {
+    _emailController.dispose();
+    super.dispose();
+  }
+
+  void _submitForm() {
+    if (_formKey.currentState!.validate()) {
+      context.read<AuthenticationBloc>().add(
+        AuthenticationRequestSignInCodeRequested(
+          email: _emailController.text.trim(),
+        ),
+      );
+    }
+  }
+
+  @override
+  Widget build(BuildContext context) {
+    final l10n = context.l10n;
+
+    return Form(
+      key: _formKey,
+      child: Column(
+        crossAxisAlignment: CrossAxisAlignment.stretch,
+        children: [
+          TextFormField(
+            controller: _emailController,
+            decoration: InputDecoration(
+              labelText: l10n.authenticationEmailLabel,
+              border: const OutlineInputBorder(),
+              // Consider adding hint text if needed
+            ),
+            keyboardType: TextInputType.emailAddress,
+            autocorrect: false,
+            textInputAction: TextInputAction.done,
+            enabled: !widget.isLoading,
+            validator: (value) {
+              if (value == null || value.isEmpty || !value.contains('@')) {
+                return l10n.accountLinkingEmailValidationError;
+              }
+              return null;
+            },
+            onFieldSubmitted:
+                (_) => _submitForm(), // Allow submitting from keyboard
+          ),
+          const SizedBox(height: AppSpacing.lg),
+          ElevatedButton(
+            onPressed: widget.isLoading ? null : _submitForm,
+            child:
+                widget.isLoading
+                    ? const SizedBox(
+                      height: 24,
+                      width: 24,
+                      child: CircularProgressIndicator(strokeWidth: 2),
+                    )
+                    : Text(l10n.authenticationSendLinkButton),
+          ),
+        ],
+      ),
+    );
+  }
+}