feat: add diet entity and user lifestyle habits with data seeding support

backend/seed.yaml

@@ -9,6 +9,16 @@ roles:
   - name: reader
     description: Read-only access to analytics
 
+diets:
+  - name: normal
+    description: Standard balanced diet without specific restrictions
+  - name: vegetarian
+    description: No meat or fish; includes dairy and eggs
+  - name: vegan
+    description: Purely plant-based; no animal products
+  - name: jain
+    description: Strictly vegetarian; no root vegetables (onions, potatoes, garlic, etc.)
+
 biomarker_categories:
   - name: blood
     description: Blood cell counts and hemogram markers