sidecar: scoped photos/timeline proxy (fixes review + archive leak)

- New GET /api/sidecar/timeline — proxies PP's /api/v1/photos and
  post-filters by FileName prefix matching the user's BasePath
- Also works for review/archive views (q=review:true, q=archived:true)
- Frontend route uses /timeline to avoid Gin route conflict with
  existing /photos/:uid/marks pattern

sidecar/handlers_photos.go

@@ -0,0 +1,67 @@
+package main
+
+import (
+	"encoding/json"
+	"net/http"
+	"strings"
+
+	"github.com/gin-gonic/gin"
+)
+
+// handlePhotos proxies PhotoPrism's /api/v1/photos and then post-filters
+// the response so only photos under the caller's BasePath are returned.
+// This fixes the review/archive tab cross-user leak.
+//
+// Route: GET /api/sidecar/timeline  (behind requireSession)
+func handlePhotos(pp *ppClient) gin.HandlerFunc {
+	return func(c *gin.Context) {
+		token := ctxToken(c)
+		basePath := ctxBasePath(c)
+
+		// Forward the raw query string to PhotoPrism.
+		query := c.Request.URL.RawQuery
+
+		resp, err := pp.call(c.Request.Context(), http.MethodGet, "/api/v1/photos?"+query, token, nil)
+		if err != nil || !resp.OK {
+			c.JSON(http.StatusBadGateway, gin.H{"error": "upstream photos request failed"})
+			return
+		}
+
+		// Decode as a generic array so we can inspect Path without
+		// committing to a rigid struct (PhotoPrism's photo response
+		// varies between list/detail/search endpoints).
+		var photos []map[string]any
+		if err := json.Unmarshal(resp.Body, &photos); err != nil {
+			// If it's not an array (e.g. error, single object), pass through.
+			c.Data(resp.Status, "application/json", resp.Body)
+			return
+		}
+
+		// If the user has no BasePath (admin/empty), return as-is.
+		if basePath == "" {
+			c.JSON(http.StatusOK, photos)
+			return
+		}
+
+		prefix := basePath + "/"
+
+		// Post-filter by FileName field (originals-relative path).
+		filtered := make([]map[string]any, 0, len(photos))
+		for _, ph := range photos {
+			rawPath, ok := ph["FileName"]
+			if !ok {
+				continue
+			}
+			pathStr, ok := rawPath.(string)
+			if !ok {
+				continue
+			}
+			// Match exact basePath or basePath/...
+			if pathStr == basePath || strings.HasPrefix(pathStr, prefix) {
+				filtered = append(filtered, ph)
+			}
+		}
+
+		c.JSON(http.StatusOK, filtered)
+	}
+}