refactor: split oil price ingestion and prediction into separate services + commands

- BrentPriceFetcher owns ingestion (fetchFromEia / fetchFromFred, each throws on failure)
- BrentPricePredictor owns prediction and marks latest brent_prices row as generated
- oil:fetch command tries EIA, falls back to FRED, fails loudly if both fail
- oil:predict command prompts if latest price already has a prediction; --force bypasses
- add prediction_generated_at column to brent_prices
- delete OilPriceService (replaced by the two focused services)

tests/Unit/Services/BrentPricePredictorTest.php

@@ -0,0 +1,144 @@
+<?php
+
+use App\Enums\PredictionSource;
+use App\Enums\TrendDirection;
+use App\Models\BrentPrice;
+use App\Models\PricePrediction;
+use App\Services\BrentPricePredictor;
+use App\Services\LlmPrediction\OilPredictionProvider;
+use Illuminate\Foundation\Testing\RefreshDatabase;
+
+uses(RefreshDatabase::class);
+
+beforeEach(function (): void {
+    $this->provider = Mockery::mock(OilPredictionProvider::class);
+    $this->predictor = new BrentPricePredictor($this->provider);
+});
+
+it('detects a rising trend when 3-day EWMA exceeds 7-day EWMA by threshold', function (): void {
+    $prices = collect(range(1, 14))->map(fn (int $i) => new BrentPrice([
+        'date' => now()->subDays(14 - $i)->toDateString(),
+        'price_usd' => 70.0 + ($i * 2.0),
+    ]));
+
+    $prediction = $this->predictor->generateEwmaPrediction($prices);
+
+    expect($prediction->direction)->toBe(TrendDirection::Rising)
+        ->and($prediction->source)->toBe(PredictionSource::Ewma)
+        ->and($prediction->confidence)->toBeGreaterThan(0)
+        ->and($prediction->confidence)->toBeLessThanOrEqual(65);
+});
+
+it('detects a falling trend when 3-day EWMA falls below 7-day EWMA by threshold', function (): void {
+    $prices = collect(range(1, 14))->map(fn (int $i) => new BrentPrice([
+        'date' => now()->subDays(14 - $i)->toDateString(),
+        'price_usd' => 85.0 - ($i * 2.0),
+    ]));
+
+    $prediction = $this->predictor->generateEwmaPrediction($prices);
+
+    expect($prediction->direction)->toBe(TrendDirection::Falling);
+});
+
+it('returns flat when price movement is within threshold', function (): void {
+    $prices = collect(range(1, 14))->map(fn (int $i) => new BrentPrice([
+        'date' => now()->subDays(14 - $i)->toDateString(),
+        'price_usd' => 75.0 + (($i % 2 === 0) ? 0.1 : -0.1),
+    ]));
+
+    $prediction = $this->predictor->generateEwmaPrediction($prices);
+
+    expect($prediction->direction)->toBe(TrendDirection::Flat)
+        ->and($prediction->confidence)->toBe(50);
+});
+
+it('returns null when fewer than 14 prices are available for EWMA', function (): void {
+    $prices = collect(range(1, 10))->map(fn (int $i) => new BrentPrice([
+        'date' => now()->subDays(10 - $i)->toDateString(),
+        'price_usd' => 75.0,
+    ]));
+
+    expect($this->predictor->generateEwmaPrediction($prices))->toBeNull();
+});
+
+it('stores both EWMA and LLM predictions when provider succeeds', function (): void {
+    seedPrices(20);
+
+    $this->provider->shouldReceive('predict')->once()->andReturn(new PricePrediction([
+        'predicted_for' => now()->toDateString(),
+        'source' => PredictionSource::LlmWithContext,
+        'direction' => TrendDirection::Rising,
+        'confidence' => 70,
+        'reasoning' => 'Trend is up.',
+        'generated_at' => now(),
+    ]));
+
+    $prediction = $this->predictor->generatePrediction();
+
+    expect($prediction->source)->toBe(PredictionSource::LlmWithContext)
+        ->and(PricePrediction::count())->toBe(2);
+});
+
+it('falls back to EWMA when provider returns null', function (): void {
+    seedPrices(20, slope: 0.8);
+
+    $this->provider->shouldReceive('predict')->once()->andReturn(null);
+
+    $prediction = $this->predictor->generatePrediction();
+
+    expect($prediction->source)->toBe(PredictionSource::Ewma)
+        ->and(PricePrediction::count())->toBe(1);
+});
+
+it('returns null when there is insufficient price data', function (): void {
+    BrentPrice::insert([
+        ['date' => now()->subDays(2)->toDateString(), 'price_usd' => 75.0],
+        ['date' => now()->subDay()->toDateString(), 'price_usd' => 76.0],
+    ]);
+
+    $this->provider->shouldNotReceive('predict');
+
+    expect($this->predictor->generatePrediction())->toBeNull()
+        ->and(PricePrediction::count())->toBe(0);
+});
+
+it('flags latest brent price as prediction generated on success', function (): void {
+    seedPrices(20);
+
+    $this->provider->shouldReceive('predict')->once()->andReturn(null);
+
+    $this->predictor->generatePrediction();
+
+    $latest = BrentPrice::orderBy('date', 'desc')->first();
+
+    expect($latest->prediction_generated_at)->not->toBeNull();
+});
+
+it('does not flag when prediction cannot be generated', function (): void {
+    BrentPrice::insert([
+        ['date' => now()->subDay()->toDateString(), 'price_usd' => 75.0],
+    ]);
+
+    $this->provider->shouldNotReceive('predict');
+
+    $this->predictor->generatePrediction();
+
+    expect(BrentPrice::first()->prediction_generated_at)->toBeNull();
+});
+
+it('returns the latest price row', function (): void {
+    seedPrices(3);
+
+    expect($this->predictor->latestPrice())->not->toBeNull()
+        ->and($this->predictor->latestPrice()->date->toDateString())->toBe(now()->toDateString());
+});
+
+function seedPrices(int $count, float $slope = 1.0): void
+{
+    BrentPrice::insert(
+        collect(range(1, $count))->map(fn (int $i) => [
+            'date' => now()->subDays($count - $i)->toDateString(),
+            'price_usd' => 75.0 + ($i * $slope),
+        ])->all()
+    );
+}