feat: add postcode resolution to /api/stations and Filament SearchResource

Extends NearbyStationsRequest to accept `postcode` (full or outcode) as an alternative to lat/lng. PostcodeService resolves it via postcodes.io and falls through to coordinates. Also adds SearchResource to the Filament admin panel for viewing logged search activity with fuel type filter and price/distance stats columns. Includes SQLite GREATEST/LEAST function polyfills in AppServiceProvider for test compatibility.

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

tests/Unit/Services/OilPriceServiceTest.php

@@ -221,7 +221,7 @@ it('sends web_search tool in the context prediction request', function (): void
     Http::assertSent(function ($request) {
         $tools = $request->data()['tools'] ?? [];
 
-        return collect($tools)->contains(fn ($t) => $t['type'] === 'web_search_20260209');
+        return collect($tools)->contains(fn ($t) => $t['type'] === 'web_search_20250305');
     });
 });
 
@@ -299,7 +299,7 @@ it('uses LLM with context when API key is configured', function (): void {
     $prediction = $this->service->generatePrediction();
 
     expect($prediction->source)->toBe(PredictionSource::LlmWithContext)
-        ->and(PricePrediction::count())->toBe(1);
+        ->and(PricePrediction::count())->toBe(2);
 });
 
 it('falls back to plain LLM when context method fails', function (): void {
@@ -323,7 +323,7 @@ it('falls back to plain LLM when context method fails', function (): void {
     $prediction = $this->service->generatePrediction();
 
     expect($prediction->source)->toBe(PredictionSource::Llm)
-        ->and(PricePrediction::count())->toBe(1);
+        ->and(PricePrediction::count())->toBe(2);
 });
 
 it('falls back to EWMA when both LLM methods fail', function (): void {