Fix summarizer worker infinite loop and map AI trigger errors to safe HTTP responses.

Paginate un-summarized tenders and mark rows missing notice/folder IDs as handled so the worker cannot spin forever. Return 400/404 for validation and not-found cases on AI summarize/analyze triggers instead of leaking internal errors as 500.

internal/tender/handler.go

@@ -589,7 +589,7 @@ func (h *TenderHandler) TriggerAISummarize(c echo.Context) error {
 			"tender_id": id,
 			"error":     err.Error(),
 		})
-		return response.InternalServerError(c, err.Error())
+		return mapAITriggerHTTPError(c, err, "AI summarization")
 	}
 
 	return response.Success(c, result, "AI summarization completed successfully")
@@ -619,12 +619,28 @@ func (h *TenderHandler) TriggerAIAnalyze(c echo.Context) error {
 			"tender_id": id,
 			"error":     err.Error(),
 		})
-		return response.InternalServerError(c, err.Error())
+		return mapAITriggerHTTPError(c, err, "AI analysis")
 	}
 
 	return response.Success(c, result, "AI analysis completed successfully")
 }
 
+// mapAITriggerHTTPError maps AI trigger service errors to safe HTTP responses.
+func mapAITriggerHTTPError(c echo.Context, err error, action string) error {
+	switch {
+	case errors.Is(err, ErrEmptyTenderID), errors.Is(err, ErrInvalidTenderID):
+		return response.BadRequest(c, "Invalid request", "Invalid tender ID")
+	case errors.Is(err, ErrTenderNotFound), errors.Is(err, orm.ErrDocumentNotFound):
+		return response.NotFound(c, "Tender not found")
+	case errors.Is(err, ErrTenderMissingNoticeID), errors.Is(err, ErrTenderMissingContractFolderID):
+		return response.BadRequest(c, "Tender not eligible", "Tender is missing required identifiers for AI processing")
+	case errors.Is(err, ErrAINotConfigured):
+		return response.InternalServerError(c, "AI service is not available")
+	default:
+		return response.InternalServerError(c, action+" failed")
+	}
+}
+
 // TriggerAITranslate triggers on-demand AI translation for a tender
 // @Summary Trigger AI translation
 // @Description Trigger on-demand AI translation for tender title and description (cached in MinIO by the AI service)