Rename castle-app to libra-app

Match the upstream LNbits extension rebrand (Castle Accounting → Libra).
Renames the standalone PWA build artifacts and all references:

- castle.html → libra.html
- vite.castle.config.ts → vite.libra.config.ts (PWA name "Libra —
  Team Accounting", short_name "Libra", manifest id libra-accounting)
- npm scripts: build:castle/dev:castle/preview:castle → build:libra
  etc; dev:all and build:demo chains updated; dist-castle → dist-libra
- Hub tile: Lucide icon Castle → Scale (the scales/balance metaphor),
  label "Castle" → "Libra", env var VITE_HUB_CASTLE_URL → VITE_HUB_LIBRA_URL
- ExpensesAPI: /castle/api/v1/* → /libra/api/v1/* (matches the renamed
  LNbits extension's URL prefix)
- Feature flags VITE_CASTLE_INCOME_ENABLED/VITE_CASTLE_BUDGETS_ENABLED →
  VITE_LIBRA_*
- i18n: top-level "castle" namespace → "libra" across en/es/fr; all
  t('castle.*') usages updated
- localStorage key castle-expense-drafts → libra-expense-drafts
- nginx.conf.example: /castle/ routes + castle.<domain> redirect → libra
- Comments and identifiers: castleOwesUser → libraOwesUser, castle.api
  references in docs

Source dir src/accounting-app/ stays as-is (already feature-named, not
brand-named).

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

vite.config.ts

@@ -33,7 +33,7 @@ export default defineConfig(({ mode }) => ({
           '**/*.{js,css,html,ico,png,svg}'
         ],
         // Don't intercept standalone app paths — they have their own service workers
-        navigateFallbackDenylist: [/^\/sortir\//, /^\/castle\//, /^\/wallet\//, /^\/chat\//, /^\/market\//, /^\/cart\//, /^\/checkout\//, /^\/tasks\//, /^\/forum\//, /^\/submit\//, /^\/submission\//],
+        navigateFallbackDenylist: [/^\/sortir\//, /^\/libra\//, /^\/wallet\//, /^\/chat\//, /^\/market\//, /^\/cart\//, /^\/checkout\//, /^\/tasks\//, /^\/forum\//, /^\/submit\//, /^\/submission\//],
       },
       includeAssets: [
         'favicon.ico',