refactor(ui): R10 S4 — complete the selection-paint sweep (all pill idioms)

The first S4 pass migrated a subset, which left same-idiom selection pills
hand-rolled and made adjacent controls inconsistent (a /code-review finding).
This completes the sweep so every selected-among-options control shares the
recipe:

- plain pills → .pill (+ aria-pressed): Channels status filters + view tabs,
  Sidebar filter-tag chips + date presets + custom-dates, Stats tabs + ranges.
- glass-card-resting pills → .pill with the resting `glass-card glass-hover` kept
  in the non-pressed branch (solid accent when pressed): PlexSidebar library
  scope + the facet Chip (retired the round-1 "deferred" note — the recipe
  already expresses this via the resting branch, no new variant needed).
- custom-dates aria-pressed is coerced with !! so a date string can't leak into
  the attribute and miss the [aria-pressed="true"] paint.
- drop the dead `border` on ChannelTags' chip-solid (accent border on accent bg).

Out of scope (a separate concern, NOT selection-among-options): primary/action
buttons that share the accent fill — Banner action, ConfirmProvider primary,
PlexBrowse primary, PlayerModal watched-toggle — these want a future .btn-primary
recipe. Left by-design: tableHeader filter options (PopoverItem + keepSelectedPaint,
owned by the popover platform).

frontend/src/components/Sidebar.tsx

@@ -46,11 +46,8 @@ function TagChip({
       data-tag={tag.name}
       onClick={onClick}
       title={t("sidebar.channelCount", { count })}
-      className={`inline-flex items-center gap-1.5 text-xs px-2.5 py-1 rounded-full border shadow-xs hover:shadow-sm active:translate-y-px transition ${
-        active
-          ? "bg-accent text-accent-fg border-accent"
-          : "bg-card border-border text-fg hover:border-accent"
-      }`}
+      aria-pressed={active}
+      className="pill inline-flex items-center gap-1.5 text-xs px-2.5 py-1 rounded-full border shadow-xs hover:shadow-sm active:translate-y-px"
     >
       <span>{tag.name}</span>
       <span
@@ -169,11 +166,8 @@ export default function Sidebar({
                         dateTo: undefined,
                       })
                     }
-                    className={`text-xs px-2.5 py-1 rounded-full border shadow-xs active:translate-y-px transition ${
-                      activePreset
-                        ? "bg-accent text-accent-fg border-accent"
-                        : "bg-card border-border hover:border-accent"
-                    }`}
+                    aria-pressed={activePreset}
+                    className="pill text-xs px-2.5 py-1 rounded-full border shadow-xs active:translate-y-px"
                   >
                     {t("sidebar.datePreset." + p.key)}
                   </button>
@@ -185,11 +179,8 @@ export default function Sidebar({
                   setCustomDates(next);
                   if (next) setFilters({ ...filters, maxAgeDays: undefined });
                 }}
-                className={`text-xs px-2.5 py-1 rounded-full border shadow-xs active:translate-y-px transition ${
-                  customDates || filters.dateFrom || filters.dateTo
-                    ? "bg-accent text-accent-fg border-accent"
-                    : "bg-card border-border hover:border-accent"
-                }`}
+                aria-pressed={!!(customDates || filters.dateFrom || filters.dateTo)}
+                className="pill text-xs px-2.5 py-1 rounded-full border shadow-xs active:translate-y-px"
               >
                 {t("sidebar.custom")}
               </button>