feat: AI model selection dropdown with Claude and OpenAI models

Replaced free-text model field with Selection showing standard models
from both providers: Claude Opus/Sonnet/Haiku and OpenAI GPT-4o/4.1/o3.

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

fusion-woo-odoo/fusion_woocommerce/models/woo_instance.py

@@ -60,8 +60,20 @@ class WooInstance(models.Model):
         ('openai', 'OpenAI'),
     ], string='AI Provider')
     ai_api_key = fields.Char(string='AI API Key', groups='base.group_system')
-    ai_model = fields.Char(string='AI Model',
-        help='e.g., claude-sonnet-4-5-20250514 for Claude or gpt-4o for OpenAI')
+    ai_model = fields.Selection([
+        # Claude models
+        ('claude-opus-4-20250514', 'Anthropic — Claude Opus 4'),
+        ('claude-sonnet-4-5-20250514', 'Anthropic — Claude Sonnet 4.5'),
+        ('claude-haiku-4-5-20251001', 'Anthropic — Claude Haiku 4.5'),
+        # OpenAI models
+        ('gpt-4o', 'OpenAI — GPT-4o'),
+        ('gpt-4o-mini', 'OpenAI — GPT-4o Mini'),
+        ('gpt-4-turbo', 'OpenAI — GPT-4 Turbo'),
+        ('gpt-4.1', 'OpenAI — GPT-4.1'),
+        ('gpt-4.1-mini', 'OpenAI — GPT-4.1 Mini'),
+        ('gpt-4.1-nano', 'OpenAI — GPT-4.1 Nano'),
+        ('o3-mini', 'OpenAI — o3 Mini'),
+    ], string='AI Model')
 
     # AI Prompts
     prompt_product_title = fields.Text(string='Product Title Prompt',