feat(settings): data-safe editors, deep-linked search, Data/About/Cost pages

- EditorModal loads once per path (a parent re-render no longer reloads the
  file over the user's typing), refuses Save after a failed load, opens a
  truncated (>256 KB) file read-only, and asks before overwriting a file
  that changed on disk or could not be re-read.
- Settings/Hooks editors unset only keys from the snapshot taken at Edit,
  warn when the file changed underneath, keep a renamed key's value, and
  refuse a new key named like a redacted one (env) or a read-only hook
  event, which used to replace the secret/hooks.
- Project scope shows its resolved folder and is disabled inside the
  plugin cache. Account-profile, pricing-row and pet deletes confirm;
  two-click actions disarm after 3 s; unsaved drafts ask before closing.
- Search indexes every Claude Code / Codex sub-tab, opens it via ?tab= and
  scrolls to + highlights the row; the active config tab is in the URL.
- General splits into General / Data / About; Pricing moves to a Cost
  group with one shared load; config tabs group as Content / Extensions /
  Config with arrow-key roving; Promise.allSettled per tab.
- Data: browser-preferences export/import (allowlisted keys), per-section
  reset, housekeeping dry-run first, clear-all behind a typed phrase.
  Server: purge days must be a whole number >= 1 (INVALID_PURGE_DAYS) and
  dry_run returns exactly what the real run would delete.
- Alerts can be edited; webhooks/alerts/remote-source failures toast;
  copies go through copyText; modals get dialog roles and useDialog.
- Sagi: Ctrl/Cmd+B only when shown and not typing, default spot clear of
  row controls, arrow keys move it, reduced motion honoured; the dead
  /run launch link goes to the workspace.

client/src/components/settings/AppearanceSettings.tsx

@@ -5,13 +5,16 @@
  * `index.css`). Each card's swatch re-scopes the theme's CSS variables on its
  * own element (`dark` class or `data-mode`, plus `data-theme`), so the preview
  * is painted by the same tokens as the app — no hex is duplicated here.
+ * **Reset to defaults** (after a confirm) returns to Dark with both stock themes.
  * @author Nguyễn Ngọc Trí Vĩ <vinnt@smartgift.vn>
  */
 
 import { useTranslation } from "react-i18next";
-import { Monitor, Moon, Sun } from "lucide-react";
+import { Monitor, Moon, RotateCcw, Sun } from "lucide-react";
 import { SettingsRow, SettingsSegmented } from "./SettingsRow";
 import { THEMES, useTheme, type Theme, type ThemeMode } from "../../hooks/useTheme";
+import { confirmDialog } from "../../lib/confirm";
+import { toast } from "../../lib/toast";
 
 const THEME_LABELS: Record<string, string> = {
   darcula: "Darcula",
@@ -61,6 +64,19 @@ export function AppearanceSettings() {
   const { t } = useTranslation("settings");
   const { mode, theme, themeFor, setMode, setThemeFor } = useTheme();
 
+  const reset = async () => {
+    const ok = await confirmDialog({
+      title: t("appearance.resetTitle"),
+      message: t("appearance.resetBody"),
+      confirmLabel: t("appearance.reset"),
+    });
+    if (!ok) return;
+    setMode("dark");
+    setThemeFor("dark", "default");
+    setThemeFor("light", "default");
+    toast.success(t("appearance.resetDone"));
+  };
+
   return (
     <div className="card p-5 space-y-5">
       <SettingsRow
@@ -116,6 +132,13 @@ export function AppearanceSettings() {
           </div>
         </div>
       ))}
+
+      <div className="flex justify-end border-t border-border pt-3">
+        <button type="button" onClick={() => void reset()} className="btn-ghost text-xs">
+          <RotateCcw className="w-3.5 h-3.5" />
+          {t("appearance.reset")}
+        </button>
+      </div>
     </div>
   );
 }