Remove prediction API endpoint and integrate into stations search

Consolidate prediction functionality by merging /api/prediction endpoint into /api/stations response. Move prediction logic from PredictionController into StationController, returning prediction data alongside station results. Replace usePrediction composable with unified useStations that returns {stations, meta, prediction}. Remove PredictionRequest, related tests, and unused Vue components (FuelFinderTest, MapTest, RecommendationTest, StationListTest). Add PredictionFull component and UpsellBanner. Extend NationalFuelPredictionService to include weekly_summary (7-day series, yesterday/today averages, cheapest/priciest days) and oil signal from price_predictions table. Update Home.vue to consume prediction from stations response. Add Plan::resolveCadenceForUser helper and configure Cashier to use custom Subscription model.

app/Http/Requests/Api/PredictionRequest.php

@@ -1,21 +0,0 @@
-<?php
-
-namespace App\Http\Requests\Api;
-
-use Illuminate\Foundation\Http\FormRequest;
-
-class PredictionRequest extends FormRequest
-{
-    public function authorize(): bool
-    {
-        return true;
-    }
-
-    public function rules(): array
-    {
-        return [
-            'lat' => ['nullable', 'numeric', 'between:-90,90'],
-            'lng' => ['nullable', 'numeric', 'between:-180,180'],
-        ];
-    }
-}