feat(sign-in): replace alert() with inline status on email sign-in button

Removes the debug alert() calls from the email magic-link flow.
Button now shows live feedback inline:
- 'Sending…' while the lookup is in flight (disabled + cursor-wait)
- 'Email sent ✓' on success (green fill)
- 'No account found' if no user matches the email
- 'Error — retry?' on network/API failure
- 'Enter an email first' if submitted empty
Clicking the button while showing a result resets it to the default label.

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

src/lib/app_components/e_app_sign_in_out.svelte

@@ -73,6 +73,9 @@
     let is_changing_password = $state(false);
     let show_password_text = $state('password'); // password or text
 
+    // Email sign-in status: null | 'sending' | 'sent' | 'not_found' | 'error'
+    let email_send_status: null | string = $state(null);
+
     function sign_in() {
         $ae_loc.jwt = user_obj.jwt; // Store the JSON Web Token
         $ae_loc.person_id = person_id; // Set the person_id in the ae_loc store
@@ -231,17 +234,19 @@
             .then((user_response) => {
                 if (user_response?.user_id_random) {
                     console.log(`User found for email:`, user_response);
-                    handle_send_auth_email({
+                    handle_send_auth_email({ user_id: user_response.user_id_random });
-                        user_id: user_response.user_id_random
+                    email_send_status = 'sent';
-                    });
                 } else if (user_response && user_response.length > 0) {
                     console.log(`Multiple users found for email:`, user_response);
-                    handle_send_auth_email({
+                    handle_send_auth_email({ user_id: user_response[0].user_id_random });
-                        user_id: user_response[0].user_id_random
+                    email_send_status = 'sent';
-                    });
                 } else {
-                    alert('No user found with that email address.');
+                    console.warn('No user found for email:', email);
+                    email_send_status = 'not_found';
                 }
+            })
+            .catch(() => {
+                email_send_status = 'error';
             });
     }
 
@@ -378,12 +383,12 @@
                 onsubmit={async (e) => {
                     e.preventDefault();
                     if ($ae_sess.auth__entered_email) {
-                        alert('Attempting to look up user by email address.');
+                        email_send_status = 'sending';
                         handle_lookup_user_email({
                             email: $ae_sess.auth__entered_email
                         });
                     } else {
-                        alert('Please enter an email address to look up.');
+                        email_send_status = 'no_email';
                     }
                 }}
             >
@@ -397,11 +402,31 @@
                 />
                 <button
                     type="submit"
-                    class="btn btn-sm preset-tonal-secondary border border-secondary-500 hover:preset-filled-secondary-500 w-full justify-center"
+                    class="btn btn-sm w-full justify-center transition-all
+                        {email_send_status === 'sent'    ? 'preset-filled-success-500'
+                        : email_send_status === 'sending' ? 'preset-tonal-surface opacity-70 cursor-wait'
+                        : email_send_status === 'not_found' || email_send_status === 'error' ? 'preset-tonal-error border border-error-500'
+                        : 'preset-tonal-secondary border border-secondary-500 hover:preset-filled-secondary-500'}"
+                    disabled={email_send_status === 'sending'}
                     title="Look up user by email and send sign in email"
+                    onclick={() => { email_send_status = null; }}
                 >
                     <MailCheck size="1em" class="shrink-0" />
-                    <span class="ml-1">Send Sign In Email</span>
+                    <span class="ml-1">
+                        {#if email_send_status === 'sending'}
+                            Sending…
+                        {:else if email_send_status === 'sent'}
+                            Email sent ✓
+                        {:else if email_send_status === 'not_found'}
+                            No account found
+                        {:else if email_send_status === 'error'}
+                            Error — retry?
+                        {:else if email_send_status === 'no_email'}
+                            Enter an email first
+                        {:else}
+                            Send Sign In Email
+                        {/if}
+                    </span>
                 </button>
             </form>