Chat bubbles, icons for chats, more vivid and distinct colour tags

- Bubbles: own messages right-aligned in their own colour, agent answers left.
- Chat icons (22, validated on the server), shown in list, top bar, project page.
- Colour tags: eight fixed hues (new: pink) with theme-matched lightness and the
  highest chroma sRGB allows; stronger background tint.

Co-Authored-By: Claude Sonnet 5.5 <noreply@anthropic.com>

server/src/jobs.rs

@@ -323,6 +323,7 @@ pub async fn run_with(app: &Arc<App>, job: &Job, trigger: &str, payload: Option<
         telegram_quiet: true,
         summary: String::new(),
         color: None,
+        icon: None,
     };
     let session = app.save_session(session)?;
     app.store.job_started(&job.id, &session.id, now)?;