refactor(ui/alerts): tighter inbox action bar, history uses global time range

Inbox: replace 4 parallel outlined buttons with 2 context-aware ones.
When nothing is selected → "Acknowledge all firing" (primary) + "Mark all
read" (secondary). When rows are selected → the same slots become
"Acknowledge N" + "Mark N read" with counts inlined. Primary variant
gives the foreground action proper visual weight; secondary is the
supporting action. No more visually-identical disabled buttons cluttering
the bar.

History: drop the local DateRangePicker. The page now reads
`timeRange` from `useGlobalFilters()` so the top-bar TimeRangeDropdown
(1h / 3h / 6h / Today / 24h / 7d / custom) is the single source of
truth, consistent with every other time-scoped page in the app.

ui/src/pages/Alerts/HistoryPage.tsx

@@ -1,8 +1,7 @@
-import { useState } from 'react';
 import { Link } from 'react-router';
 import { History } from 'lucide-react';
 import {
-  DataTable, EmptyState, DateRangePicker,
+  DataTable, EmptyState, useGlobalFilters,
 } from '@cameleer/design-system';
 import type { Column } from '@cameleer/design-system';
 import { PageLoader } from '../../components/PageLoader';
@@ -29,18 +28,16 @@ function formatDuration(from?: string | null, to?: string | null): string {
 }
 
 export default function HistoryPage() {
-  const [dateRange, setDateRange] = useState({
-    start: new Date(Date.now() - 7 * 24 * 3600_000),
-    end: new Date(),
-  });
+  const { timeRange } = useGlobalFilters();
 
-  // useAlerts doesn't accept a time range today; filter client-side.
+  // useAlerts doesn't accept a time range today; filter client-side
+  // against the global TimeRangeDropdown in the top bar.
   const { data, isLoading, error } = useAlerts({ state: 'RESOLVED', limit: 200 });
 
   const filtered = (data ?? []).filter((a) => {
     if (!a.firedAt) return false;
     const t = new Date(a.firedAt).getTime();
-    return t >= dateRange.start.getTime() && t <= dateRange.end.getTime();
+    return t >= timeRange.start.getTime() && t <= timeRange.end.getTime();
   });
 
   const columns: Column<AlertDto>[] = [
@@ -95,9 +92,6 @@ export default function HistoryPage() {
               : `${filtered.length} resolved alert${filtered.length === 1 ? '' : 's'} in range`}
           </span>
         </div>
-        <div className={css.pageActions}>
-          <DateRangePicker value={dateRange} onChange={setDateRange} />
-        </div>
       </header>
 
       {filtered.length === 0 ? (

ui/src/pages/Alerts/InboxPage.tsx

@@ -200,38 +200,47 @@ export default function InboxPage() {
           {allSelected ? 'Deselect all' : `Select all${rows.length ? ` (${rows.length})` : ''}`}
         </label>
         <span style={{ flex: 1 }} />
-        <Button
-          variant="secondary"
-          size="sm"
-          onClick={() => onBulkAck(selectedFiringIds)}
-          disabled={selectedFiringIds.length === 0 || ack.isPending}
-        >
-          Acknowledge selected
-        </Button>
-        <Button
-          variant="secondary"
-          size="sm"
-          onClick={() => onBulkAck(firingIds)}
-          disabled={firingIds.length === 0 || ack.isPending}
-        >
-          Acknowledge all firing
-        </Button>
-        <Button
-          variant="secondary"
-          size="sm"
-          onClick={() => onBulkRead(selectedIds)}
-          disabled={selectedIds.length === 0 || bulkRead.isPending}
-        >
-          Mark selected read
-        </Button>
-        <Button
-          variant="secondary"
-          size="sm"
-          onClick={() => onBulkRead(unreadIds)}
-          disabled={unreadIds.length === 0 || bulkRead.isPending}
-        >
-          Mark all read
-        </Button>
+        {selectedIds.length > 0 ? (
+          <>
+            <Button
+              variant="primary"
+              size="sm"
+              onClick={() => onBulkAck(selectedFiringIds)}
+              disabled={selectedFiringIds.length === 0 || ack.isPending}
+            >
+              {selectedFiringIds.length > 0
+                ? `Acknowledge ${selectedFiringIds.length}`
+                : 'Acknowledge selected'}
+            </Button>
+            <Button
+              variant="secondary"
+              size="sm"
+              onClick={() => onBulkRead(selectedIds)}
+              disabled={bulkRead.isPending}
+            >
+              Mark {selectedIds.length} read
+            </Button>
+          </>
+        ) : (
+          <>
+            <Button
+              variant="primary"
+              size="sm"
+              onClick={() => onBulkAck(firingIds)}
+              disabled={firingIds.length === 0 || ack.isPending}
+            >
+              Acknowledge all firing
+            </Button>
+            <Button
+              variant="secondary"
+              size="sm"
+              onClick={() => onBulkRead(unreadIds)}
+              disabled={unreadIds.length === 0 || bulkRead.isPending}
+            >
+              Mark all read
+            </Button>
+          </>
+        )}
       </div>
 
       {rows.length === 0 ? (