feat: build out the /plugins page

The nav and footer have linked to /plugins since the start, but no
route or page existed, so it rendered blank. Adds the page per the
docs/PAGES.md spec — plugin building blocks, the four built-in
plugins, a step-by-step "writing a plugin" guide with real code from
netork/plugins/, and the fire/call/transform hook bus — sourced from
the actual plugin system in the main NetOrk repo for accuracy.

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

src/i18n/translations.ts

@@ -254,6 +254,20 @@ const en = {
     groupPlanned: 'Planned',
     groupConsidering: 'Under consideration',
   },
+  plugins: {
+    heading: 'Plugin System',
+    sub: 'Integrations are plugins, not core code. Wazuh, Graylog, CrowdSec, and apt-cacher-ng all register through the same pattern — metadata, hooks, tasks, router.',
+    whatHeading: 'What is a plugin?',
+    builtinHeading: 'Built-in plugins',
+    writingHeading: 'Writing a plugin',
+    hookBusHeading: 'Hook bus',
+    registryHeading: 'Plugin registry & enable/disable',
+    cta: {
+      heading: 'Add your own integration.',
+      body: 'One documented pattern — metadata, hooks, tasks, router. No core code changes required.',
+      button: 'Get started →',
+    },
+  },
   nis2: {
     heading: 'NIS2 & netOrk',
     sub: 'NIS2 Art. 21 defines ten categories of technical and organizational measures. Some of them are directly addressed by what netOrk does every day. This page maps each requirement to netOrk\'s current capabilities — honestly, including what\'s partial and what\'s not applicable.',
@@ -537,6 +551,20 @@ const de: Translations = {
     groupPlanned: 'Geplant',
     groupConsidering: 'In Erwägung',
   },
+  plugins: {
+    heading: 'Plugin-System',
+    sub: 'Integrationen sind Plugins, kein Core-Code. Wazuh, Graylog, CrowdSec und apt-cacher-ng registrieren sich alle über dasselbe Muster — Metadaten, Hooks, Tasks, Router.',
+    whatHeading: 'Was ist ein Plugin?',
+    builtinHeading: 'Eingebaute Plugins',
+    writingHeading: 'Ein Plugin schreiben',
+    hookBusHeading: 'Hook-Bus',
+    registryHeading: 'Plugin-Registry & Aktivieren/Deaktivieren',
+    cta: {
+      heading: 'Eigene Integration hinzufügen.',
+      body: 'Ein dokumentiertes Muster — Metadaten, Hooks, Tasks, Router. Keine Änderungen am Core-Code nötig.',
+      button: 'Loslegen →',
+    },
+  },
   nis2: {
     heading: 'NIS2 & netOrk',
     sub: 'NIS2 Art. 21 definiert zehn Kategorien technischer und organisatorischer Maßnahmen. Einige werden durch das, was netOrk täglich tut, direkt adressiert. Diese Seite ordnet jede Anforderung den aktuellen netOrk-Funktionen zu — ehrlich, einschließlich was teilweise abgedeckt ist und was nicht anwendbar ist.',