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>

src/i18n/mod.rs

@@ -174,8 +174,8 @@ pub fn t(locale: Locale, key: &str) -> String {
 ///
 /// ```
 /// use dashboard::i18n::{tw, Locale};
-/// let text = tw(Locale::En, "chat.minutes_ago", &[("n", "5")]);
-/// assert_eq!(text, "5m ago");
+/// let text = tw(Locale::En, "common.up_to_seats", &[("n", "5")]);
+/// assert_eq!(text, "Up to 5 seats");
 /// ```
 pub fn tw(locale: Locale, key: &str, vars: &[(&str, &str)]) -> String {
     let mut result = t(locale, key);
@@ -221,8 +221,8 @@ mod tests {
 
     #[test]
     fn variable_substitution() {
-        let result = tw(Locale::En, "chat.minutes_ago", &[("n", "5")]);
-        assert_eq!(result, "5m ago");
+        let result = tw(Locale::En, "common.up_to_seats", &[("n", "5")]);
+        assert_eq!(result, "Up to 5 seats");
     }
 
     #[test]