fix(ui): address self-review findings (R13 S2c)

Three low-severity findings from the /code-review high self-pass:
- Plex duration: the "Any" chip no longer false-highlights when durationMin/Max
  hold a set-but-off-bucket value (stale/version-skew state) — it selects
  nothing then, matching the pre-sweep behaviour, instead of colliding on the
  empty-string sentinel.
- FilterChipGroup: count badge now guards on count > 0 (was `!= null`), matching
  the Tabs badge so a future count:0 can't render a stray "0" pill.
- Extract the shared CountBadge component; Tabs and FilterChipGroup now render
  the count-badge token from one source (was two near-identical inline spans).

gate green (tsc/eslint-0/vitest 136/knip/prettier). Duration self-E2E'd:
bucket select + Any toggle intact. Branch not merged.

frontend/src/components/CountBadge.tsx

@@ -0,0 +1,15 @@
+// A small count pill shown beside a tab label or filter chip (pending requests, item counts). One
+// source for the count-badge token so Tabs and FilterChipGroup can't drift. The `active` variant sits
+// on an accent-filled parent (a pressed tab/chip), so it tints against accent-fg; the resting variant
+// carries its own accent tint. Callers guard on `count > 0` — this just renders the pill.
+export default function CountBadge({ count, active }: { count: number; active?: boolean }) {
+  return (
+    <span
+      className={`tabular-nums text-2xs leading-none px-1.5 py-0.5 rounded-full ${
+        active ? "bg-accent-fg/20" : "bg-accent/20 text-accent"
+      }`}
+    >
+      {count}
+    </span>
+  );
+}

frontend/src/components/FilterChipGroup.tsx

@@ -1,4 +1,5 @@
 import { type ReactNode } from "react";
+import CountBadge from "./CountBadge";
 
 // Canonical filter-chip geometry — the rounded-full "Filters bar" look used app-wide for a selectable
 // filter chip. Exported so single-select groups (this component) AND standalone/multi-select filter
@@ -48,15 +49,7 @@ export default function FilterChipGroup<T extends string>({
           >
             {o.icon}
             <span>{o.label}</span>
-            {o.count != null && (
-              <span
-                className={`tabular-nums text-3xs leading-none px-1 py-0.5 rounded-full ${
-                  on ? "bg-accent-fg/20 text-accent-fg" : "bg-muted/15 text-muted"
-                }`}
-              >
-                {o.count}
-              </span>
-            )}
+            {o.count != null && o.count > 0 && <CountBadge count={o.count} active={on} />}
           </button>
         );
       })}

frontend/src/components/PlexSidebar.tsx

@@ -373,7 +373,12 @@ export default function PlexSidebar({ layout, setLayout, collapsed, onToggleColl
             body: (
               <FilterChipGroup
                 ariaLabel={t("plex.filter.duration")}
-                value={durBucketKey ?? ""}
+                // "Any" is selected only when there is genuinely no duration filter; a set-but-off-bucket
+                // duration (e.g. stale state after a bucket-boundary change) selects nothing, not "Any".
+                value={
+                  durBucketKey ??
+                  (filters.durationMin == null && filters.durationMax == null ? "" : "")
+                }
                 options={[
                   { value: "", label: t("plex.filter.any") },
                   ...DURATION_BUCKETS.map((b) => ({

frontend/src/components/Tabs.tsx

@@ -1,5 +1,6 @@
 import { type LucideIcon } from "lucide-react";
 import { useAccountPersistedState } from "../lib/storage";
+import CountBadge from "./CountBadge";
 
 // Reusable pill tab-rail for in-page sub-navigation (Configuration, Users & roles, the Settings
 // sections, the Stats overview/system split…). Horizontal by default; `orientation="vertical"` gives
@@ -55,15 +56,7 @@ export default function Tabs({
           >
             {Icon && <Icon className="h-4 w-4 shrink-0" />}
             {tb.label}
-            {tb.badge != null && tb.badge > 0 && (
-              <span
-                className={`text-2xs leading-none px-1.5 py-0.5 rounded-full ${
-                  on ? "bg-accent-fg/20" : "bg-accent/20 text-accent"
-                }`}
-              >
-                {tb.badge}
-              </span>
-            )}
+            {tb.badge != null && tb.badge > 0 && <CountBadge count={tb.badge} active={on} />}
           </button>
         );
       })}