feat: Add host-based assistant avatars (Neko/Mochi)

- Add avatar field to hosts.json config for Neko and Mochi
- Create HostContext to provide host config to components
- Display host avatar and name in chat messages instead of generic Claude
- Add user avatar and first name to user messages
- Include avatar in /api/hosts endpoint response
- Fix appendFileSync import for debug logging

🤖 Generated with [Claude Code](https://claude.com/claude-code)

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

backend/server.js

@@ -4,7 +4,7 @@ import { createServer } from 'http';
 import { spawn } from 'child_process';
 import { v4 as uuidv4 } from 'uuid';
 import cors from 'cors';
-import { existsSync, readFileSync, readdirSync, statSync, mkdirSync, writeFileSync } from 'fs';
+import { existsSync, readFileSync, readdirSync, statSync, mkdirSync, writeFileSync, appendFileSync } from 'fs';
 import { join, basename, extname } from 'path';
 import multer from 'multer';
 import session from 'express-session';
@@ -171,6 +171,7 @@ app.get('/api/hosts', requireAuth, (req, res) => {
     id,
     name: host.name,
     description: host.description,
+    avatar: host.avatar,
     color: host.color,
     icon: host.icon,
     connectionType: host.connection.type,
@@ -845,8 +846,7 @@ wss.on('connection', async (ws, req) => {
               event
             };
             try {
-              const fs = await import('fs');
-              fs.appendFileSync(debugLogPath, JSON.stringify(debugEntry) + '\n');
+              appendFileSync(debugLogPath, JSON.stringify(debugEntry) + '\n');
             } catch (e) {
               // Ignore write errors
             }