refactor(usage): fold claude-desktop into claude in the dashboard

The Desktop gateway's proxy traffic is still recorded under its own
app_type for route-takeover billing audit (the request detail panel
shows the real value), but the dashboard now folds it into `claude`
for display. A standalone "Claude Desktop" bucket only ever showed a
partial number: Desktop chat usage never passes through the proxy and
has no scannable local source, while its Code-tab sessions are just the
embedded Claude Code runtime writing into the shared ~/.claude/projects
tree — so a separate bucket misled users into reading it as Desktop's
full usage.

Backend: new `folded_app_type_sql` helper wraps the app_type column in
every dashboard read path (10 filter sites + the by-app projection) so
`= 'claude'` also matches claude-desktop and GROUP BY merges the two,
without changing bound-param counts. Dedup matching and provider-limit
checks keep exact comparison; get_request_logs folds only the WHERE
filter and keeps the raw app_type in its row projection.

Frontend: drop claude-desktop from the dashboard AppType/KNOWN_APP_TYPES
filter list, the UsageHero theme, and the now-dead appFilter locale key
in all four languages (the managed-app apps.claude-desktop label stays).

Adds test_claude_desktop_folds_into_claude_for_display.

src/types/usage.ts

@@ -141,28 +141,26 @@ export interface UsageRangeSelection {
 }
 
 /**
- * App types whose token usage is reliably collected by the proxy.
+ * App types surfaced as dashboard filter buttons.
  *
- * `claude-desktop` was previously hidden because its rows looked like pure
- * failure noise — that was an accounting bug: streaming/transform usage of
- * the Desktop gateway was logged under app_type "claude", leaving only
- * edge-case rows under "claude-desktop". The backend now attributes all
- * Desktop traffic to "claude-desktop", so it is a first-class filter option.
+ * `claude-desktop` is intentionally NOT listed: the Desktop gateway's proxy
+ * traffic is still recorded under its own `app_type` (preserving route-takeover
+ * billing audit — the request detail panel shows the real value), but the
+ * dashboard folds it into `claude` for display. It is the embedded Claude Code
+ * runtime running inside the Desktop shell, and Desktop *chat* usage never
+ * passes through this app at all, so a separate "Claude Desktop" bucket would
+ * only ever show a partial number and mislead users into reading it as the
+ * Desktop's full usage. The backend collapses `claude-desktop → claude` in
+ * every dashboard query (see `folded_app_type_sql`).
  * `opencode` / `openclaw` / `hermes` have no proxy handler at all — they
  * appear only as managed apps elsewhere.
  */
-export type AppType =
-  | "claude"
-  | "claude-desktop"
-  | "codex"
-  | "gemini"
-  | "opencode";
+export type AppType = "claude" | "codex" | "gemini" | "opencode";
 
 export type AppTypeFilter = "all" | AppType;
 
 export const KNOWN_APP_TYPES: ReadonlyArray<AppType> = [
   "claude",
-  "claude-desktop",
   "codex",
   "gemini",
   "opencode",