feat(settings): Open Source Licenses section in System tab (#477)

* feat(licenses): tooling and initial data generation

Adds the maintainer-only generator that produces src/data/licenses.json:
- src-tauri/about.toml + about.hbs: cargo-about config + handlebars template
  for the Rust-side license enumeration
- scripts/generate-licenses.mjs: orchestrator that runs cargo-about and
  license-checker-rseidelsohn (via npx, no devDep), merges the outputs into
  a single per-crate JSON with full license texts, and writes the result to
  src/data/licenses.json

The script is invoked directly with `node scripts/generate-licenses.mjs` —
no npm script wrapper on purpose, since adding one to package.json would
trigger the nix-npm-deps-hash-sync workflow on every push.

Initial generation covers 575 cargo crates + 71 npm packages (646 entries
total, all with full license text bundled, ~1.4 MB JSON).

* feat(licenses): Settings panel UI

Adds a new Open Source Licenses section under Settings → System,
sitting below Contributors. Components:

- LicensesPanel.tsx: search input, curated highlight block of ~10 key
  dependencies (Tauri, React, rodio, symphonia, etc.), TanStack-Virtual
  list of all 600+ entries
- LicenseTextModal.tsx: full-screen-ish modal showing the bundled license
  text plus name/version/license-id badges + repository link
- licensesData.ts: lazy dynamic-import loader (Vite emits the JSON as a
  separate chunk, so the heavy ~1.4 MB payload is only loaded when the
  user actually opens the panel — no runtime fetch, the data is fixed
  into the build artifact)

The panel registers itself in the Settings in-page search index under
the System tab.

* feat(licenses): i18n in 8 locales

Adds the `licenses` namespace (title, intro, highlights, search
placeholder, no-results, loading / load error, no-license-text,
view-source, total line, generated-at) across en, de, fr, nl, zh, nb,
ru, es. License names themselves (MIT, Apache-2.0, GPL-3.0, …) stay
universal and are rendered as-is.

* docs(release): document licenses regeneration step

Adds a Step A.3 to the release SOP describing the maintainer-only
`node scripts/generate-licenses.mjs` workflow, the cargo-about
prerequisite, and explicitly notes why no npm script wrapper exists
(would trigger the nix-npm-deps-hash-sync workflow).

src/locales/de.ts

@@ -1796,4 +1796,17 @@ export const deTranslation = {
     exitPsysonic: 'Psysonic beenden',
     nothingPlaying: 'Nichts wird abgespielt',
   },
+  licenses: {
+    title: 'Open-Source-Lizenzen',
+    intro: 'Psysonic basiert auf Open-Source-Software. Die untenstehende Liste zeigt jede Abhängigkeit, die mit der App ausgeliefert wird, inklusive Version, Lizenz und vollständigem Lizenztext.',
+    highlights: 'Wichtige Abhängigkeiten',
+    searchPlaceholder: 'Suche nach Name, Version oder Lizenz…',
+    noResults: 'Keine Treffer.',
+    loading: 'Lizenzen werden geladen…',
+    loadError: 'Lizenzdaten konnten nicht geladen werden.',
+    noLicenseText: 'Für diese Abhängigkeit ist kein Lizenztext gebündelt.',
+    viewSource: 'Quelle anzeigen',
+    totalLine: '{{total}} Abhängigkeiten — {{cargo}} Cargo, {{npm}} npm',
+    generatedAt: 'Zuletzt generiert {{date}}',
+  },
 };

src/locales/en.ts

@@ -1803,4 +1803,17 @@ export const enTranslation = {
     exitPsysonic: 'Exit Psysonic',
     nothingPlaying: 'Nothing playing',
   },
+  licenses: {
+    title: 'Open Source Licenses',
+    intro: 'Psysonic is built on open-source software. The list below shows every dependency that ships in the app, with its version, license, and full license text.',
+    highlights: 'Key dependencies',
+    searchPlaceholder: 'Search by name, version or license…',
+    noResults: 'No matches.',
+    loading: 'Loading licenses…',
+    loadError: 'Could not load license data.',
+    noLicenseText: 'No license text bundled for this dependency.',
+    viewSource: 'View source',
+    totalLine: '{{total}} dependencies — {{cargo}} cargo, {{npm}} npm',
+    generatedAt: 'Last generated {{date}}',
+  },
 };

src/locales/es.ts

@@ -1765,4 +1765,17 @@ export const esTranslation = {
     exitPsysonic: 'Salir de Psysonic',
     nothingPlaying: 'Nada en reproducción',
   },
+  licenses: {
+    title: 'Licencias de Código Abierto',
+    intro: 'Psysonic se basa en software de código abierto. La lista siguiente muestra cada dependencia incluida con la aplicación, con su versión, licencia y el texto completo de la licencia.',
+    highlights: 'Dependencias principales',
+    searchPlaceholder: 'Buscar por nombre, versión o licencia…',
+    noResults: 'Sin resultados.',
+    loading: 'Cargando licencias…',
+    loadError: 'No se pudieron cargar los datos de licencia.',
+    noLicenseText: 'No hay texto de licencia incluido para esta dependencia.',
+    viewSource: 'Ver fuente',
+    totalLine: '{{total}} dependencias — {{cargo}} cargo, {{npm}} npm',
+    generatedAt: 'Última generación {{date}}',
+  },
 };

src/locales/fr.ts

@@ -1760,4 +1760,17 @@ export const frTranslation = {
     exitPsysonic: 'Quitter Psysonic',
     nothingPlaying: 'Aucune lecture',
   },
+  licenses: {
+    title: 'Licences Open Source',
+    intro: 'Psysonic est construit sur des logiciels open source. La liste ci-dessous montre chaque dépendance livrée avec l\'application, avec sa version, sa licence et le texte de licence complet.',
+    highlights: 'Dépendances principales',
+    searchPlaceholder: 'Rechercher par nom, version ou licence…',
+    noResults: 'Aucun résultat.',
+    loading: 'Chargement des licences…',
+    loadError: 'Impossible de charger les données de licence.',
+    noLicenseText: 'Aucun texte de licence groupé pour cette dépendance.',
+    viewSource: 'Voir la source',
+    totalLine: '{{total}} dépendances — {{cargo}} cargo, {{npm}} npm',
+    generatedAt: 'Dernière génération {{date}}',
+  },
 };

src/locales/nb.ts

@@ -1759,4 +1759,17 @@ export const nbTranslation = {
     exitPsysonic: 'Avslutt Psysonic',
     nothingPlaying: 'Ingenting spilles',
   },
+  licenses: {
+    title: 'Åpen kildekode-lisenser',
+    intro: 'Psysonic er bygget på åpen kildekode-programvare. Listen nedenfor viser hver avhengighet som leveres med appen, med versjon, lisens og full lisenstekst.',
+    highlights: 'Sentrale avhengigheter',
+    searchPlaceholder: 'Søk etter navn, versjon eller lisens…',
+    noResults: 'Ingen treff.',
+    loading: 'Laster lisenser…',
+    loadError: 'Kunne ikke laste inn lisensdata.',
+    noLicenseText: 'Ingen lisenstekst inkludert for denne avhengigheten.',
+    viewSource: 'Vis kilde',
+    totalLine: '{{total}} avhengigheter — {{cargo}} cargo, {{npm}} npm',
+    generatedAt: 'Sist generert {{date}}',
+  },
 };

src/locales/nl.ts

@@ -1759,4 +1759,17 @@ export const nlTranslation = {
     exitPsysonic: 'Psysonic afsluiten',
     nothingPlaying: 'Niets wordt afgespeeld',
   },
+  licenses: {
+    title: 'Open-source licenties',
+    intro: 'Psysonic is gebouwd op open-source software. De onderstaande lijst toont elke afhankelijkheid die met de app wordt meegeleverd, met versie, licentie en volledige licentietekst.',
+    highlights: 'Belangrijke afhankelijkheden',
+    searchPlaceholder: 'Zoek op naam, versie of licentie…',
+    noResults: 'Geen resultaten.',
+    loading: 'Licenties laden…',
+    loadError: 'Licentiegegevens konden niet worden geladen.',
+    noLicenseText: 'Geen licentietekst meegeleverd voor deze afhankelijkheid.',
+    viewSource: 'Bron bekijken',
+    totalLine: '{{total}} afhankelijkheden — {{cargo}} cargo, {{npm}} npm',
+    generatedAt: 'Laatst gegenereerd {{date}}',
+  },
 };

src/locales/ru.ts

@@ -1846,4 +1846,17 @@ export const ruTranslation = {
     exitPsysonic: 'Закрыть Psysonic',
     nothingPlaying: 'Ничего не воспроизводится',
   },
+  licenses: {
+    title: 'Лицензии открытого кода',
+    intro: 'Psysonic построен на программном обеспечении с открытым исходным кодом. Список ниже показывает каждую зависимость, поставляемую с приложением, с версией, лицензией и полным текстом лицензии.',
+    highlights: 'Ключевые зависимости',
+    searchPlaceholder: 'Поиск по имени, версии или лицензии…',
+    noResults: 'Нет совпадений.',
+    loading: 'Загрузка лицензий…',
+    loadError: 'Не удалось загрузить данные о лицензиях.',
+    noLicenseText: 'Текст лицензии для этой зависимости не включён.',
+    viewSource: 'Открыть исходник',
+    totalLine: '{{total}} зависимостей — {{cargo}} cargo, {{npm}} npm',
+    generatedAt: 'Последняя генерация {{date}}',
+  },
 };

src/locales/zh.ts

@@ -1752,4 +1752,17 @@ export const zhTranslation = {
     exitPsysonic: '退出 Psysonic',
     nothingPlaying: '当前没有播放',
   },
+  licenses: {
+    title: '开源许可证',
+    intro: 'Psysonic 基于开源软件构建。下方列表显示了应用程序中包含的每个依赖项的版本、许可证以及完整的许可证文本。',
+    highlights: '主要依赖项',
+    searchPlaceholder: '按名称、版本或许可证搜索…',
+    noResults: '没有匹配项。',
+    loading: '加载许可证…',
+    loadError: '无法加载许可证数据。',
+    noLicenseText: '此依赖项未包含许可证文本。',
+    viewSource: '查看源代码',
+    totalLine: '{{total}} 个依赖项 — {{cargo}} cargo, {{npm}} npm',
+    generatedAt: '最后生成时间 {{date}}',
+  },
 };