fix: resolve image upload issues in posts

- Dashboard: disable submit button during uploads, show upload errors, guard against pending uploads
- Filament: add maxParallelUploads(1) to fix race condition (filamentphp#13306)
- Filament: add image/webp to gallery acceptedFileTypes, increase resize 30->50
- Dashboard: add image/webp to gallery input accept
- Add missing notifications table migration for Filament databaseNotifications

database/migrations/2026_09_18_021743_create_notifications_table.php

@@ -0,0 +1,31 @@
+<?php
+
+use Illuminate\Database\Migrations\Migration;
+use Illuminate\Database\Schema\Blueprint;
+use Illuminate\Support\Facades\Schema;
+
+return new class extends Migration
+{
+    /**
+     * Run the migrations.
+     */
+    public function up(): void
+    {
+        Schema::create('notifications', function (Blueprint $table) {
+            $table->uuid('id')->primary();
+            $table->string('type');
+            $table->morphs('notifiable');
+            $table->text('data');
+            $table->timestamp('read_at')->nullable();
+            $table->timestamps();
+        });
+    }
+
+    /**
+     * Reverse the migrations.
+     */
+    public function down(): void
+    {
+        Schema::dropIfExists('notifications');
+    }
+};