feat(chat): replace built-in chat with LibreChat SSO integration

Replaces the custom chat page with an external LibreChat instance that
shares Keycloak SSO for seamless auto-login. Removes Tools and Knowledge
Base pages as these are now handled by LibreChat's built-in capabilities.

- Add LibreChat service to docker-compose with Ollama backend config
- Add Keycloak OIDC client (certifai-librechat) with prompt=none for
  silent SSO
- Create librechat.yaml with CERTifAI branding, Ollama endpoint, and
  custom page title/logo
- Change sidebar Chat link to external URL (opens LibreChat in new tab)
- Remove chat page, tools page, knowledge base page and all related
  components (chat_sidebar, chat_bubble, chat_input_bar, etc.)
- Remove tool_card, file_row components and tool/knowledge models
- Remove chat_stream SSE handler (no longer needed)
- Clean up i18n files: remove chat, tools, knowledge sections
- Dashboard article summarization via Ollama remains intact

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

assets/i18n/de.json

@@ -38,8 +38,6 @@
     "dashboard": "Dashboard",
     "providers": "Provider",
     "chat": "Chat",
-    "tools": "Werkzeuge",
-    "knowledge_base": "Wissensdatenbank",
     "developer": "Entwickler",
     "organization": "Organisation",
     "switch_light": "Zum hellen Modus wechseln",
@@ -72,28 +70,6 @@
     "trending": "Im Trend",
     "recent_searches": "Letzte Suchen"
   },
-  "chat": {
-    "new_chat": "Neuer Chat",
-    "general": "Allgemein",
-    "conversations": "Unterhaltungen",
-    "news_chats": "Nachrichten-Chats",
-    "all_chats": "Alle Chats",
-    "no_conversations": "Noch keine Unterhaltungen",
-    "type_message": "Nachricht eingeben...",
-    "model_label": "Modell:",
-    "no_models": "Keine Modelle verfuegbar",
-    "send_to_start": "Senden Sie eine Nachricht, um die Unterhaltung zu starten.",
-    "you": "Sie",
-    "assistant": "Assistent",
-    "thinking": "Denkt nach...",
-    "copy_response": "Letzte Antwort kopieren",
-    "copy_conversation": "Unterhaltung kopieren",
-    "edit_last": "Letzte Nachricht bearbeiten",
-    "just_now": "gerade eben",
-    "minutes_ago": "vor {n} Min.",
-    "hours_ago": "vor {n} Std.",
-    "days_ago": "vor {n} T."
-  },
   "providers": {
     "title": "Provider",
     "subtitle": "Konfigurieren Sie Ihre LLM- und Embedding-Backends",
@@ -107,37 +83,6 @@
     "active_config": "Aktive Konfiguration",
     "embedding": "Embedding"
   },
-  "tools": {
-    "title": "Werkzeuge",
-    "subtitle": "MCP-Server und Werkzeugintegrationen verwalten",
-    "calculator": "Taschenrechner",
-    "calculator_desc": "Mathematische Berechnungen und Einheitenumrechnung",
-    "tavily": "Tavily-Suche",
-    "tavily_desc": "KI-optimierte Websuche-API fuer Echtzeitinformationen",
-    "searxng": "SearXNG",
-    "searxng_desc": "Datenschutzfreundliche Metasuchmaschine",
-    "file_reader": "Dateileser",
-    "file_reader_desc": "Lokale Dateien in verschiedenen Formaten lesen und analysieren",
-    "code_executor": "Code-Ausfuehrer",
-    "code_executor_desc": "Isolierte Codeausfuehrung fuer Python und JavaScript",
-    "web_scraper": "Web-Scraper",
-    "web_scraper_desc": "Strukturierte Daten aus Webseiten extrahieren",
-    "email_sender": "E-Mail-Versand",
-    "email_sender_desc": "E-Mails ueber konfigurierten SMTP-Server versenden",
-    "git_ops": "Git-Operationen",
-    "git_ops_desc": "Mit Git-Repositories fuer Versionskontrolle interagieren"
-  },
-  "knowledge": {
-    "title": "Wissensdatenbank",
-    "subtitle": "Dokumente fuer RAG-Abfragen verwalten",
-    "search_placeholder": "Dateien suchen...",
-    "name": "Name",
-    "type": "Typ",
-    "size": "Groesse",
-    "chunks": "Abschnitte",
-    "uploaded": "Hochgeladen",
-    "actions": "Aktionen"
-  },
   "developer": {
     "agents_title": "Agent Builder",
     "agents_desc": "Erstellen und verwalten Sie KI-Agenten mit LangGraph. Erstellen Sie mehrstufige Schlussfolgerungspipelines, werkzeugnutzende Agenten und autonome Workflows.",