Answer the inbox from the panel, with templates

A reply starts from a template filled in the language the person wrote in,
is sent by the application when it has a mailer that delivers or handed to
the replier's mail program otherwise, and is recorded on the submission.
The same is available through the API.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

app/Models/ApplicationReply.php

@@ -0,0 +1,31 @@
+<?php
+
+declare(strict_types=1);
+
+namespace App\Models;
+
+use Illuminate\Database\Eloquent\Attributes\Fillable;
+use Illuminate\Database\Eloquent\Model;
+use Illuminate\Database\Eloquent\Relations\BelongsTo;
+
+/**
+ * An answer given to a submission, kept so the next person to open it knows
+ * what was already said.
+ */
+#[Fillable(['user_id', 'user_name', 'subject', 'body', 'channel'])]
+class ApplicationReply extends Model
+{
+    public const UPDATED_AT = null;
+
+    public const MAIL = 'mail';
+
+    public const MAILTO = 'mailto';
+
+    /**
+     * @return BelongsTo<Application, $this>
+     */
+    public function application(): BelongsTo
+    {
+        return $this->belongsTo(Application::class);
+    }
+}