Show only the photographs taken in the period you are looking at

The library could be narrowed by rating, flag and availability, but not
by when a photograph was taken — so finding a fortnight meant scrolling
to it and holding position.

The range rides on `RatingFilter` for the reason `local_only` already
does: every query path threads that one struct, so the count in the
header cannot claim a total the grid does not draw. Undated images are
excluded whenever either end is set — they cannot be inside or outside a
span, and drawing them made the range look as though it had not applied.

Taken from the timeline rather than typed into two date fields. Finding
the period is what the histogram is for, and having found it the user
should not have to read the dates off the axis and key them back in.
The histogram keeps drawing the full extent while the range is on, or
there would be nowhere to widen back out from.

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

ui/dr-ui/ui/app.slint

@@ -387,6 +387,9 @@ export component AppWindow inherits Window {
     in-out property <bool> library-local-only: false;
     in property <int> library-local-count: 0;
     callback library-toggle-local-only();
+    /// Whether the grid is narrowed to the timeline's visible span.
+    in-out property <bool> library-range-active: false;
+    callback library-toggle-date-range();
     callback library-retry-connection();
 
     // --- pinning a collection offline (FR-NC-6a) ---
@@ -997,6 +1000,8 @@ in property <bool> panel-visible: true;
                     local-only: root.library-local-only;
                     local-count: root.library-local-count;
                     toggle-local-only() => { root.library-toggle-local-only(); }
+                    range-active: root.library-range-active;
+                    toggle-date-range() => { root.library-toggle-date-range(); }
 
                     collections-visible: root.collections-visible;
                     toggle-collections() => { root.toggle-collections(); }

ui/dr-ui/ui/library.slint

@@ -846,6 +846,9 @@ export component LibraryGrid inherits Rectangle {
     in property <bool> local-only: false;
     in property <int> local-count: 0;
     callback toggle-local-only();
+    /// Whether the grid is narrowed to the timeline's visible span.
+    in property <bool> range-active: false;
+    callback toggle-date-range();
 
     /// How many images are selected, for the header's count.
     in property <int> selected-count: 0;
@@ -1240,6 +1243,23 @@ export component LibraryGrid inherits Rectangle {
                     clicked => { root.toggle-local-only(); }
                 }
 
+                Rectangle { width: Theme.gap; }
+
+                // Narrow the grid to the span the timeline is showing. The
+                // histogram is already how you find a period, so the range is
+                // taken from it rather than typed: zoom to the fortnight you
+                // want, then say "only that". Clicking again lifts it.
+                //
+                // The histogram deliberately keeps drawing the full extent
+                // while this is on, or there would be nothing left to widen
+                // back out from.
+                FilterChip {
+                    label: root.range-active ? "Date range ×" : "Limit to range";
+                    active: root.range-active;
+                    y: (parent.height - self.height) / 2;
+                    clicked => { root.toggle-date-range(); }
+                }
+
                 Rectangle { horizontal-stretch: 1; }
 
                 // What the filter is currently hiding. Without this a narrowed