feat: add per-app usage filtering (Claude/Codex/Gemini)

Add dashboard-level app type filter to usage statistics, replacing the
DataSourceBar with a more useful segmented control. All components
(summary cards, trend chart, provider stats, model stats, request logs)
now respond to the selected app filter.

Backend: add optional app_type parameter to get_usage_summary,
get_daily_trends, get_provider_stats, and get_model_stats queries.
Frontend: new AppTypeFilter type, updated query keys with appType
dimension for proper cache separation, and RequestLogTable local
filter auto-locks when dashboard filter is active.

src/components/usage/RequestLogTable.tsx

@@ -29,6 +29,7 @@ import {
 } from "./format";
 
 interface RequestLogTableProps {
+  appType?: string;
   refreshIntervalMs: number;
 }
 
@@ -37,7 +38,10 @@ const MAX_FIXED_RANGE_SECONDS = 30 * ONE_DAY_SECONDS;
 
 type TimeMode = "rolling" | "fixed";
 
-export function RequestLogTable({ refreshIntervalMs }: RequestLogTableProps) {
+export function RequestLogTable({
+  appType: dashboardAppType,
+  refreshIntervalMs,
+}: RequestLogTableProps) {
   const { t, i18n } = useTranslation();
   const queryClient = useQueryClient();
 
@@ -56,8 +60,14 @@ export function RequestLogTable({ refreshIntervalMs }: RequestLogTableProps) {
   const pageSize = 20;
   const [validationError, setValidationError] = useState<string | null>(null);
 
+  // When dashboard-level app filter is active (not "all"), override the local appType filter
+  const dashboardAppTypeActive = dashboardAppType && dashboardAppType !== "all";
+  const effectiveFilters: LogFilters = dashboardAppTypeActive
+    ? { ...appliedFilters, appType: dashboardAppType }
+    : appliedFilters;
+
   const { data: result, isLoading } = useRequestLogs({
-    filters: appliedFilters,
+    filters: effectiveFilters,
     timeMode: appliedTimeMode,
     rollingWindowSeconds: ONE_DAY_SECONDS,
     page,
@@ -174,13 +184,18 @@ export function RequestLogTable({ refreshIntervalMs }: RequestLogTableProps) {
       <div className="flex flex-col gap-4 rounded-lg border bg-card/50 p-4 backdrop-blur-sm">
         <div className="flex flex-wrap items-center gap-3">
           <Select
-            value={draftFilters.appType || "all"}
+            value={
+              dashboardAppTypeActive
+                ? dashboardAppType
+                : draftFilters.appType || "all"
+            }
             onValueChange={(v) =>
               setDraftFilters({
                 ...draftFilters,
                 appType: v === "all" ? undefined : v,
               })
             }
+            disabled={!!dashboardAppTypeActive}
           >
             <SelectTrigger className="w-[130px] bg-background">
               <SelectValue placeholder={t("usage.appType")} />