feat: implement Mistral OCR document parsing with fuzzy matching and frontend integration

backend/sample.config.yaml

@@ -10,6 +10,7 @@ paths:
   database: "./data/zhealth.db"
   logs: "./logs"
   uploads: "./data/uploads"
+  max_upload_mb: 50  # Maximum file upload size in MB
 
 logging:
   level: "info"  # Options: trace | debug | info | warn | error
@@ -29,3 +30,12 @@ ai:
   provider: "gemini"  # Options: gemini | openai | anthropic
   model: "gemini-3-flash-preview"
   api_key: "${AI_API_KEY}"
+
+# Mistral OCR for document parsing
+mistral:
+  api_key: "${MISTRAL_API_KEY}"
+  ocr_model: "mistral-ocr-latest"
+  max_pages_per_request: 8
+  max_retries: 2        # Max retry attempts per chunk
+  timeout_secs: 120     # Request timeout in seconds
+