feat: add Filament admin panel with migrations and design spec

- Add AdminPanelProvider mounting panel at `/admin` with `is_admin` auth guard
- Add `is_admin` boolean column to users table
- Add brent_prices and price_predictions tables with appropriate indexes
- Add comprehensive admin design spec covering resources, dashboard, navigation, and build order
- Configure default panel with amber primary color and standard middleware stack
- Add compiled Filament assets (actions.js, app.css)

database/migrations/2026_04_04_115852_create_brent_prices_table.php

@@ -0,0 +1,27 @@
+<?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('brent_prices', function (Blueprint $table) {
+            $table->date('date')->primary();
+            $table->decimal('price_usd')->comment('Brent crude spot price in USD per barrel');
+        });
+    }
+
+    /**
+     * Reverse the migrations.
+     */
+    public function down(): void
+    {
+        Schema::dropIfExists('brent_prices');
+    }
+};

database/migrations/2026_04_04_115852_create_price_predictions_table.php

@@ -0,0 +1,34 @@
+<?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('price_predictions', function (Blueprint $table) {
+            $table->id();
+            $table->date('predicted_for')->comment('The date this prediction covers');
+            $table->enum('source', ['llm', 'ewma']);
+            $table->enum('direction', ['rising', 'falling', 'flat']);
+            $table->tinyInteger('confidence')->unsigned()->comment('0–100 confidence score');
+            $table->text('reasoning')->nullable()->comment('LLM explanation or EWMA summary');
+            $table->datetime('generated_at');
+
+            $table->index(['predicted_for', 'source']);
+        });
+    }
+
+    /**
+     * Reverse the migrations.
+     */
+    public function down(): void
+    {
+        Schema::dropIfExists('price_predictions');
+    }
+};

database/migrations/2026_04_04_123728_add_is_admin_to_users_table.php

@@ -0,0 +1,28 @@
+<?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::table('users', function (Blueprint $table) {
+            $table->boolean('is_admin')->default(false)->after('remember_token');
+        });
+    }
+
+    /**
+     * Reverse the migrations.
+     */
+    public function down(): void
+    {
+        Schema::table('users', function (Blueprint $table) {
+            $table->dropColumn('is_admin');
+        });
+    }
+};