feat(metadata,people): richer metadata editing + face-naming flow

Metadata (sidebar):
- New editable fields: Title, Credits section (Artist/Copyright/
  License via Details), GPS Altitude.
- Video facts in the File section: Duration, FPS, Codec — required
  fixing videoFile(): PhotoPrism serializes MediaType as the bare word
  "video", so the old startsWith('video/') check never matched and the
  helper always fell back to the JPEG poster.
- Timezone correctness: buildTakenAtPatch no longer forces
  TakenAtLocal=UTC; it preserves the photo's existing UTC↔local offset
  (per-photo in bulk edits) so PhotoPrism can't clobber manual date
  edits when recomputing from TimeZone, and Year/Month/Day now derive
  from local wall-clock time.

People (was "disabled" — really: zero subjects because naming is what
creates a person, and the UI had no naming flow; prod has 40k face
markers in 790 unnamed clusters):
- Sidecar GET /api/sidecar/subjects — scoped people list via one
  markers→files→photos SQL pass (labels pattern), replacing the
  client-side probe-per-subject N+1 filter.
- Sidecar GET /api/sidecar/faces/unnamed — the caller's unnamed face
  clusters with count, crop thumb, and a representative marker UID.
- "Name new faces" panel on /tags/people: face-crop cards with inline
  name input; naming uses PhotoPrism's own flow (PUT /markers/:uid
  {Name, SubjSrc:manual}, verified against PP source) which creates
  the Subject and propagates across the cluster.
- Scoped proxy: marker PUT / subject-clear DELETE now allowed with
  per-marker ownership checks (was blanket-forbidden, which would have
  blocked naming for scoped users).
- Per-photo People chips in the sidebar from named Files[].Markers,
  linking to the person's page.

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

sidecar/handlers_ppproxy.go

@@ -185,6 +185,27 @@ func proxyToken(r *http.Request) string {
 	return r.Header.Get("X-Session-ID")
 }
 
+// markerWithinBase reports whether a marker's underlying photo lives under
+// base. Fails closed: no DB handle or unknown marker → false.
+func markerWithinBase(ppDb *gorm.DB, markerUID, base string) bool {
+	if ppDb == nil || markerUID == "" {
+		return false
+	}
+	var n int64
+	err := ppDb.Table("markers m").
+		Joins("JOIN files f ON f.file_uid = m.file_uid").
+		Joins("JOIN photos p ON p.photo_uid = f.photo_uid").
+		Where("m.marker_uid = ?", markerUID).
+		Where("p.deleted_at IS NULL").
+		Where("p.photo_path = ? OR p.photo_path LIKE ?", base, base+"/%").
+		Count(&n).Error
+	if err != nil {
+		slog.Warn("pp-proxy: marker ownership query failed", "err", err)
+		return false
+	}
+	return n > 0
+}
+
 // batchUIDsWithinBase validates that every photo UID in a batch body lives
 // under base, using one SQL query against PhotoPrism's photos table. Fails
 // closed: no DB handle, unknown UIDs, or any path outside base → false.
@@ -344,13 +365,28 @@ func handlePPProxy(cfg *Config, ppDb *gorm.DB) gin.HandlerFunc {
 
 		// Albums (heaps), labels, subjects, faces: shared across users by
 		// design in CE — reads and mutations pass through; the photos inside
-		// any of them stay path-scoped by the rules above.
+		// any of them stay path-scoped by the rules above. Note that naming
+		// a face (marker PUT below) creates/updates a shared Subject the
+		// same way album/label edits are shared.
 		case rest == "albums" || strings.HasPrefix(rest, "albums/") ||
 			rest == "labels" || strings.HasPrefix(rest, "labels/") ||
 			rest == "subjects" || strings.HasPrefix(rest, "subjects/") ||
 			rest == "faces" || strings.HasPrefix(rest, "faces/"):
 			proxy.ServeHTTP(c.Writer, c.Request)
 
+		// Marker mutations (face naming / clearing): ownership-checked —
+		// the marker's file must belong to a photo under the caller's
+		// BasePath. This is how the web client names people (PhotoPrism's
+		// own naming flow is PUT /markers/:uid {Name, SubjSrc:"manual"}).
+		case (method == http.MethodPut && strings.HasPrefix(rest, "markers/") && strings.Count(rest, "/") == 1) ||
+			(method == http.MethodDelete && strings.HasPrefix(rest, "markers/") && strings.HasSuffix(rest, "/subject")):
+			markerUID := strings.TrimSuffix(strings.TrimPrefix(rest, "markers/"), "/subject")
+			if !markerWithinBase(ppDb, markerUID, base) {
+				c.AbortWithStatusJSON(http.StatusNotFound, gin.H{"error": "marker not found"})
+				return
+			}
+			proxy.ServeHTTP(c.Writer, c.Request)
+
 		default:
 			slog.Info("pp-proxy: blocked", "user", user.UserName, "method", method, "path", rest)
 			forbid(c)