fix(qt): size the filter flyout to its content, not to 372px

The Slint original sized a fixed card around THREE source chips. This
port now has five — Plex plus the two media servers — and the row ran
to the card's edge, with the last chip all but touching the border.

The 372px becomes a floor and the width is derived from the widest chip
row plus the 16px padding on each side, capped so the card can never run
past the left edge. That also survives a UI-scale bump or a language
whose labels are longer, neither of which a fixed number can.

`implicitWidth` is safe to measure here: a Row sums its children and a
non-wrapping Text reports its natural width, so nothing in the chain
reads the card width back and there is no binding loop. An invisible
chip contributes nothing, so the card is narrower when a server is not
configured.

cc

crates/qbz-qt/qml/views/local/LocalFilterPopup.qml

@@ -1,7 +1,16 @@
 // Albums quality/format/source filter popup (LocalLibraryView.slint:2470 —
 // the component at the end of the file). Floats OVER the content: a
-// click-out backdrop plus a 372px card pinned 36px from the right edge,
-// 92px down, radius 10, surface-card, 1px subtle border.
+// click-out backdrop plus a card pinned 36px from the right edge, 92px down,
+// radius 10, surface-card, 1px subtle border.
+//
+// The card's 372px is a FLOOR, not the width. The Slint original sized a fixed
+// card around three source chips; this port grew to five (Plex plus the two
+// media servers) and the row overflowed the card — owner report, 2026-08-20.
+// The width is derived from the widest chip row instead, so it also survives a
+// UI-scale bump or a language whose labels are longer, neither of which a fixed
+// number can. `implicitWidth` is safe to measure here: a `Row` sums its
+// children and a non-wrapping `Text` reports its natural width, so nothing in
+// the chain reads the card width back and there is no binding loop.
 //
 // Three sections of FilterChips: Quality (Hi-Res / CD / Lossy), Format
 // (FLAC ALAC APE WAV, then MP3 AAC Other), Source (Local / Offline cache /
@@ -32,9 +41,19 @@ Item {
     }
 
     Rectangle {
+        id: card
         x: parent.width - width - 36
         y: 92
-        width: 372
+        /// Widest row, plus the 16px padding on each side. Capped so the card
+        /// can never run past the left edge of the window.
+        readonly property real contentWidth: Math.max(
+            titleText.implicitWidth + (root.view.filterCount > 0 ? clearBtn.width + 8 : 0),
+            qualityRow.implicitWidth,
+            formatRow1.implicitWidth,
+            formatRow2.implicitWidth,
+            sourceRow.implicitWidth)
+        width: Math.min(Math.max(372, card.contentWidth + 32),
+                        Math.max(372, root.width - 72))
         height: col.height + 32
         color: theme.surfaceCard
         radius: 10
@@ -59,6 +78,7 @@ Item {
                 width: parent.width
                 height: 28
                 Text {
+                    id: titleText
                     width: parent.width - (root.view.filterCount > 0 ? clearBtn.width : 0)
                     height: parent.height
                     text: QbzSession.tr("Filter", QbzSession.trRev)
@@ -100,6 +120,7 @@ Item {
                 font.weight: theme.weightSemibold
             }
             Row {
+                id: qualityRow
                 spacing: 8
                 FilterChip {
                     label: QbzSession.tr("Hi-Res", QbzSession.trRev)
@@ -126,6 +147,7 @@ Item {
                 font.weight: theme.weightSemibold
             }
             Row {
+                id: formatRow1
                 spacing: 8
                 FilterChip { label: "FLAC"; active: root.view.filter.flac === true; onToggled: root.view.toggleFilter("flac") }
                 FilterChip { label: "ALAC"; active: root.view.filter.alac === true; onToggled: root.view.toggleFilter("alac") }
@@ -133,6 +155,7 @@ Item {
                 FilterChip { label: "WAV"; active: root.view.filter.wav === true; onToggled: root.view.toggleFilter("wav") }
             }
             Row {
+                id: formatRow2
                 spacing: 8
                 FilterChip { label: "MP3"; active: root.view.filter.mp3 === true; onToggled: root.view.toggleFilter("mp3") }
                 FilterChip { label: "AAC"; active: root.view.filter.aac === true; onToggled: root.view.toggleFilter("aac") }
@@ -151,6 +174,7 @@ Item {
                 font.weight: theme.weightSemibold
             }
             Row {
+                id: sourceRow
                 spacing: 8
                 FilterChip {
                     label: QbzSession.tr("Local", QbzSession.trRev)