refactor(locale): move hardcoded UI strings into english locale

Adds optional namespaces (common, errors, commandPalette, headTitle,
notifications, schedule, events, home, reader, routes, badgePreview,
badgeWall) and extends existing ones (settings.*, lists.*, tools.*,
user.*, hololive.*) on the Locale interface. New fields are optional
so japanese.ts can omit them; svelte-i18n's fallbackLocale handles
the runtime miss.

HeadTitle gains an optional routeKey prop for type-safe lookup.
defaultActions becomes a factory so the command palette re-reads
locale on language toggle. The existing JP feedback translation
in routes/settings is preserved via japanese.ts.

Out of scope (kept hardcoded): service-worker.ts, app.html,
Landing*.svelte, tools.ts registry, Easter Event 2025 pages.

1 files changed, 1 insertions, 1 deletions

diff --git a/src/lib/Settings/SettingCheckboxToggle.svelte b/src/lib/Settings/SettingCheckboxToggle.svelte
index 85b4f0cd..1f58520d 100644
--- a/src/lib/Settings/SettingCheckboxToggle.svelte
+++ b/src/lib/Settings/SettingCheckboxToggle.svelte
@@ -10,7 +10,7 @@ type SettingsBooleanKeys = BooleanSettingsKeys<Settings>;
 
 export let sectionBreak = false;
 export let disabled = false;
-export let text: string | (() => string);
+export let text: string | undefined | (() => string);
 export let setting: SettingsBooleanKeys[keyof SettingsBooleanKeys];
 export let lineBreak = true;
 export let onChange: () => void = () => {