feat(settings,index): per-user index sub-path, strip dead PP settings, scope duplicates

Lets a user pick a sub-folder under their library as a working index root,
stored server-side (new sidecar user_prefs table). The Library tree, reindex,
and both duplicate views (stacks + cross-folder scan) now re-root to it via a
single userLibraryBase() helper. Also fixes the cross-folder scan/archive
endpoints, which previously walked/touched the whole originals root instead
of being scoped per-user (archive now rejects out-of-scope paths, 403).

Removes PhotoPrism settings (Search/Maps/Server-UI/Features/Import) that only
steered PhotoPrism's own bundled SPA and were never read by mulimage's UI.

Also fixes the Library tree occasionally getting stuck on "Loading folders…"
by dropping gcTime:0 and gating the spinner on isLoading instead of isPending.

Co-Authored-By: Claude Sonnet 5 <noreply@anthropic.com>

sidecar/handlers_prefs.go

@@ -0,0 +1,117 @@
+package main
+
+import (
+	"errors"
+	"net/http"
+	"os"
+	"strings"
+	"time"
+
+	"github.com/gin-gonic/gin"
+	"gorm.io/gorm"
+)
+
+// Per-user preferences the PhotoPrism account model can't hold. Currently a
+// single field — the index sub-path the web client re-roots the Library tree
+// to and scopes the reindex to. Stored in the sidecar's own DB keyed by
+// username (see UserPref in db.go); never touches PhotoPrism's auth_users.
+
+// prefsBody is the wire shape for GET responses and PUT requests alike.
+type prefsBody struct {
+	IndexPath string `json:"indexPath"`
+}
+
+// loadUserPref reads the row for a user, returning a zero-value pref (empty
+// IndexPath) when none exists yet — the "whole folder" default.
+func loadUserPref(db *gorm.DB, userName string) (UserPref, error) {
+	var p UserPref
+	err := db.Where("user_name = ?", userName).First(&p).Error
+	if errors.Is(err, gorm.ErrRecordNotFound) {
+		return UserPref{UserName: userName}, nil
+	}
+	return p, err
+}
+
+func handlePrefsGet(db *gorm.DB) gin.HandlerFunc {
+	return func(c *gin.Context) {
+		p, err := loadUserPref(db, ctxUserName(c))
+		if err != nil {
+			c.JSON(http.StatusInternalServerError, gin.H{"error": err.Error()})
+			return
+		}
+		c.JSON(http.StatusOK, prefsBody{IndexPath: p.IndexPath})
+	}
+}
+
+// handlePrefsPut validates the requested index sub-path lives under the user's
+// BasePath (an existing directory, no traversal) and upserts it. An empty
+// string clears the sub-path back to "whole folder".
+func handlePrefsPut(cfg *Config, db *gorm.DB) gin.HandlerFunc {
+	return func(c *gin.Context) {
+		var body prefsBody
+		if err := c.ShouldBindJSON(&body); err != nil {
+			c.JSON(http.StatusBadRequest, gin.H{"error": "invalid body"})
+			return
+		}
+
+		// Normalise to originals-relative, no leading/trailing slashes —
+		// the same shape the web client and auth_users.base_path use.
+		sub := strings.Trim(strings.TrimSpace(body.IndexPath), "/")
+
+		if sub != "" {
+			// The sub-path is relative to the user's BasePath; resolve the
+			// combined originals-relative path and require it to be an
+			// existing directory inside the originals root. resolveUnderRoot
+			// already rejects traversal and symlink escapes.
+			base := strings.Trim(ctxBasePath(c), "/")
+			combined := sub
+			if base != "" {
+				combined = base + "/" + sub
+			}
+			abs, err := resolveUnderRoot(cfg.OriginalsRoot, combined, true)
+			if err != nil {
+				c.JSON(http.StatusBadRequest, gin.H{"error": "invalid index path: " + err.Error()})
+				return
+			}
+			info, err := os.Stat(abs)
+			if err != nil || !info.IsDir() {
+				c.JSON(http.StatusBadRequest, gin.H{"error": "index path is not a folder"})
+				return
+			}
+		}
+
+		userName := ctxUserName(c)
+		p := UserPref{UserName: userName, IndexPath: sub, UpdatedAt: time.Now().UTC()}
+		// Upsert: a clear (sub == "") persists an empty string rather than
+		// deleting the row, so the GET path stays a single code branch.
+		if err := db.Save(&p).Error; err != nil {
+			c.JSON(http.StatusInternalServerError, gin.H{"error": err.Error()})
+			return
+		}
+		c.JSON(http.StatusOK, prefsBody{IndexPath: sub})
+	}
+}
+
+// effectiveLibraryRoot returns the requesting user's working library root,
+// originals-relative with no leading/trailing slash: their BasePath narrowed
+// by their chosen index sub-path (if any). Mirrors the web client's
+// `userLibraryBase()` — handlers that walk the filesystem on a user's behalf
+// (duplicate scan/archive) should scope to this instead of cfg.OriginalsRoot
+// so a narrowed root also narrows what those handlers can see or touch.
+// Returns "" for "whole library" (no BasePath and no sub-path set — today's
+// admin default).
+func effectiveLibraryRoot(c *gin.Context, db *gorm.DB) string {
+	base := strings.Trim(ctxBasePath(c), "/")
+	pref, err := loadUserPref(db, ctxUserName(c))
+	sub := ""
+	if err == nil {
+		sub = strings.Trim(pref.IndexPath, "/")
+	}
+	if sub == "" {
+		return base
+	}
+	if base == "" {
+		return sub
+	}
+	return base + "/" + sub
+}