fix(research): surface errors to UI + proceed without pages when all fetches fail

backend/internal/domain/market/research.go

@@ -14,6 +14,7 @@ import (
 
 	"marktvogt.de/backend/internal/domain/market/research"
 	"marktvogt.de/backend/internal/pkg/ai"
+	"marktvogt.de/backend/internal/pkg/apierror"
 	"marktvogt.de/backend/internal/pkg/scrape"
 	"marktvogt.de/backend/internal/pkg/search"
 )
@@ -41,17 +42,17 @@ func (h *ResearchHandler) Research(c *gin.Context) {
 
 	id, err := uuid.Parse(c.Param("id"))
 	if err != nil {
-		c.JSON(http.StatusBadRequest, gin.H{"error": "invalid market ID"})
+		c.JSON(http.StatusBadRequest, apierror.NewResponse(apierror.BadRequest("invalid_id", "invalid market ID")))
 		return
 	}
 
 	m, err := h.service.GetByID(ctx, id)
 	if err != nil {
 		if errors.Is(err, ErrMarketNotFound) {
-			c.JSON(http.StatusNotFound, gin.H{"error": "market not found"})
+			c.JSON(http.StatusNotFound, apierror.NewResponse(apierror.NotFound("market")))
 		} else {
 			slog.ErrorContext(ctx, "research: get market failed", "market_id", id, "err", err)
-			c.JSON(http.StatusInternalServerError, gin.H{"error": "internal error"})
+			c.JSON(http.StatusInternalServerError, apierror.NewResponse(apierror.Internal("failed to load market")))
 		}
 		return
 	}
@@ -69,25 +70,29 @@ func (h *ResearchHandler) Research(c *gin.Context) {
 		if errors.As(err, &pe) {
 			switch pe.Code {
 			case ai.ErrRateLimited:
-				c.JSON(http.StatusServiceUnavailable, gin.H{"error": "rate limited"})
+				c.JSON(http.StatusServiceUnavailable, apierror.NewResponse(apierror.BadRequest("rate_limited", "KI rate limit erreicht, bitte kurz warten")))
 				return
 			case ai.ErrSchemaViolation:
 				slog.ErrorContext(ctx, "research schema violation", "market_id", id, "raw", pe.RawOutput, "inner", pe.Inner)
-				c.JSON(http.StatusInternalServerError, gin.H{"error": "model returned invalid output"})
+				c.JSON(http.StatusInternalServerError, apierror.NewResponse(apierror.Internal("Modell hat ungültige Ausgabe geliefert")))
 				return
-			case ai.ErrInternal, ai.ErrQuotaExceeded, ai.ErrTimeout, ai.ErrInvalidRequest, ai.ErrUnavailable:
-				// fall through to generic 500
+			case ai.ErrInvalidRequest:
+				slog.ErrorContext(ctx, "research invalid request", "market_id", id, "err", pe.Message)
+				c.JSON(http.StatusInternalServerError, apierror.NewResponse(apierror.Internal("KI-Anfrage ungültig: "+pe.Message)))
+				return
+			case ai.ErrInternal, ai.ErrQuotaExceeded, ai.ErrTimeout, ai.ErrUnavailable:
+				// fall through to generic message
 			}
 		}
 		slog.ErrorContext(ctx, "research failed", "market_id", id, "err", err)
-		c.JSON(http.StatusInternalServerError, gin.H{"error": "research failed"})
+		c.JSON(http.StatusInternalServerError, apierror.NewResponse(apierror.Internal("llm enrich: "+err.Error())))
 		return
 	}
 
 	var raw llmOutput
 	if err := json.Unmarshal(out.Raw, &raw); err != nil {
 		slog.ErrorContext(ctx, "research: unmarshal LLM output failed", "market_id", id, "err", err)
-		c.JSON(http.StatusInternalServerError, gin.H{"error": "internal error"})
+		c.JSON(http.StatusInternalServerError, apierror.NewResponse(apierror.Internal("Ausgabe konnte nicht verarbeitet werden")))
 		return
 	}
 

backend/internal/domain/market/research/fetch.go

@@ -2,7 +2,6 @@ package research
 
 import (
 	"context"
-	"errors"
 	"log/slog"
 	"sync"
 
@@ -44,7 +43,7 @@ func FetchAll(ctx context.Context, sc Scraper, urls []string, concurrency int) (
 	_ = g.Wait()
 
 	if len(pages) == 0 {
-		return nil, errors.New("all candidate URLs failed to fetch")
+		slog.Warn("no pages fetched; proceeding without page content")
 	}
 	return pages, nil
 }

web/src/routes/admin/maerkte/[id]/bearbeiten/+page.svelte

@@ -120,19 +120,25 @@
 			</a>
 			<h1 class="mt-1 text-2xl font-bold">Markt bearbeiten</h1>
 		</div>
-		<form
-			method="POST"
-			action="?/research"
-			use:enhance={() => {
-				researching = true;
-				return async ({ update }) => {
-					researching = false;
-					await update();
-				};
-			}}
-		>
-			<Button type="submit" variant="secondary" loading={researching}>Mit KI recherchieren</Button>
-		</form>
+		<div class="flex flex-col items-end gap-1">
+			<form
+				method="POST"
+				action="?/research"
+				use:enhance={() => {
+					researching = true;
+					return async ({ update }) => {
+						researching = false;
+						await update();
+					};
+				}}
+			>
+				<Button type="submit" variant="secondary" loading={researching}>Mit KI recherchieren</Button
+				>
+			</form>
+			{#if form?.error && !form?.research}
+				<p class="text-xs text-red-500 dark:text-red-400">{form.error}</p>
+			{/if}
+		</div>
 	</div>
 
 	{#if researchResult}