Add Mistral OCR support and imrpove img2txt API (#1957)

Introduces Mistral OCR integration in backend and updates the `AIInterfaceService` and `MistralAIService` to support new OCR options and response normalization. Updates metering cost map for OCR and annotation usage. Refactors `DriverService` to support interface-specific service aliases. Expands the puter.js `AI.img2txt` API to support flexible options and provider selection, including Mistral OCR.

Author: jelveh

package-lock.json

@@ -122,7 +122,8 @@ class AIChatService extends BaseService {
             const svc_driver = this.services.get('driver');
             for ( const provider of this.providers ) {
                 svc_driver.register_service_alias('ai-chat',
-                                provider.service_name);
+                                provider.service_name,
+                                { iface: 'puter-chat-completion' });
             }
         }
 

src/backend/src/modules/puterai/AIChatService.js

@@ -47,6 +47,35 @@ class AIInterfaceService extends BaseService {
                         source: {
                             type: 'file',
                         },
+                        model: {
+                            type: 'string',
+                            optional: true,
+                        },
+                        pages: {
+                            type: 'json',
+                            subtype: 'array',
+                            optional: true,
+                        },
+                        includeImageBase64: {
+                            type: 'flag',
+                            optional: true,
+                        },
+                        imageLimit: {
+                            type: 'number',
+                            optional: true,
+                        },
+                        imageMinSize: {
+                            type: 'number',
+                            optional: true,
+                        },
+                        bboxAnnotationFormat: {
+                            type: 'json',
+                            optional: true,
+                        },
+                        documentAnnotationFormat: {
+                            type: 'json',
+                            optional: true,
+                        },
                     },
                     result: {
                         type: {