Make Ollama prompt editable in admin AI settings

- Add prompt column to ai_settings (migration)
- AiSetting: DEFAULT_PROMPT constant + getActivePrompt() (falls back to default if empty)
- ProcessNailPolishImage: reads prompt from DB instead of hardcoded
- Admin view: textarea to edit prompt, shows active prompt, reset-to-default link

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

app/Jobs/ProcessNailPolishImage.php

@@ -33,20 +33,7 @@ class ProcessNailPolishImage implements ShouldQueue
             $ai       = AiSetting::get();
             $imageB64 = base64_encode(Storage::disk('public')->get($import->image_path));
 
-            $prompt = <<<PROMPT
-You are analyzing a nail polish or nail product bottle/container image.
-Extract exactly these three fields and respond ONLY with a valid JSON object, no explanation, no markdown:
-{
-  "name": "the full product name or color description (e.g. 'Modeling Base Calcium Neutral Pink', 'Ruby Red', 'French White')",
-  "number": "the product code or article number printed on the label or cap (digits, letters, hyphens only — e.g. '12392-7', '123', 'NP-05')",
-  "manufacturer": "the brand or company name (the logo/brand printed on the product — e.g. 'NEONAIL', 'OPI', 'essie', 'Catrice')"
-}
-Rules:
-- manufacturer = the brand/logo name (usually prominent on the label)
-- name = the descriptive product/color name (NOT the brand)
-- number = numeric or alphanumeric code (NOT the color name)
-- If a value is genuinely not visible, use null
-PROMPT;
+            $prompt = $ai->getActivePrompt();
 
             $response = Http::timeout(160)->post("{$ai->ollama_url}/api/generate", [
                 'model'  => $ai->ollama_model,