fix: enforce nlp entity weight restrictions

api/docs/nlp/README.md

@@ -82,7 +82,7 @@ For each entity in the block's pattern:
         - `Confidence` is a value between 0 and 1, returned by the NLU engine.
         - `Weight` is a configured importance factor for that specific entity type.
 - If the match is a wildcard (i.e., the block accepts any value):
-   - A **penalty factor** is applied to slightly reduce its contribution:
+    - A **penalty factor** is applied to slightly reduce its contribution:
     ``confidence × weight × penaltyFactor``. This encourages more specific matches when available.
 
 ### Scoring Formula Summary

api/src/nlp/schemas/nlp-entity.schema.ts

@@ -61,7 +61,7 @@ export class NlpEntityStub extends BaseSchema {
   /**
    * Entity's weight used to determine the next block to trigger in the conversational flow.
    */
-  @Prop({ type: Number, default: 1 })
+  @Prop({ type: Number, default: 1, min: 0 })
   weight: number;
 
   /**