fix: correct i18n SSO translations and fix validation/type issues (#29564)

Signed-off-by: NeatGuyCoding <15627489+NeatGuyCoding@users.noreply.github.com>
Co-authored-by: gemini-code-assist[bot] <176961590+gemini-code-assist[bot]@users.noreply.github.com>

api/core/entities/knowledge_entities.py

@@ -1,4 +1,4 @@
-from pydantic import BaseModel, Field
+from pydantic import BaseModel, Field, field_validator
 
 
 class PreviewDetail(BaseModel):
@@ -20,9 +20,17 @@ class IndexingEstimate(BaseModel):
 class PipelineDataset(BaseModel):
     id: str
     name: str
-    description: str | None = Field(default="", description="knowledge dataset description")
+    description: str = Field(default="", description="knowledge dataset description")
     chunk_structure: str
 
+    @field_validator("description", mode="before")
+    @classmethod
+    def normalize_description(cls, value: str | None) -> str:
+        """Coerce None to empty string so description is always a string."""
+        if value is None:
+            return ""
+        return value
+
 
 class PipelineDocument(BaseModel):
     id: str