perf: Major performance overhaul with virtual scrolling and context splitting

Phase 1 - Virtual Scrolling:
- Add @tanstack/react-virtual for efficient message list rendering
- Only render visible messages instead of entire history
- Fix auto-scroll using native scrollTop instead of unreliable virtualizer

Phase 2 - Context Optimization:
- Split monolithic SessionContext into 4 specialized contexts
- MessagesContext, SessionsContext, SettingsContext, UIContext
- Prevents unnecessary re-renders across unrelated components

Phase 3 - Compression & Cleanup:
- Enable Brotli compression (~23% smaller than gzip)
- Switch to fholzer/nginx-brotli:v1.28.0 image
- Add automatic upload cleanup for idle sessions

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

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

backend/.npmrc

@@ -0,0 +1,5 @@
+fetch-timeout=300000
+fetch-retries=3
+fetch-retry-factor=2
+fetch-retry-mintimeout=10000
+fetch-retry-maxtimeout=60000

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, appendFileSync } from 'fs';
+import { existsSync, readFileSync, readdirSync, statSync, mkdirSync, writeFileSync, appendFileSync, rmSync } from 'fs';
 import { join, basename, extname } from 'path';
 import multer from 'multer';
 import session from 'express-session';
@@ -41,6 +41,32 @@ const DEBUG = process.env.DEBUG === 'true';
 const UPLOAD_DIR = process.env.UPLOAD_DIR || '/projects/.claude-uploads';
 const MAX_FILE_SIZE = 10 * 1024 * 1024; // 10MB
 
+// History cache with 30s TTL
+const historyCache = new Map();
+const HISTORY_CACHE_TTL = 30 * 1000; // 30 seconds
+
+function getCachedHistory(cacheKey) {
+  const cached = historyCache.get(cacheKey);
+  if (cached && Date.now() - cached.timestamp < HISTORY_CACHE_TTL) {
+    return cached.data;
+  }
+  historyCache.delete(cacheKey);
+  return null;
+}
+
+function setCachedHistory(cacheKey, data) {
+  historyCache.set(cacheKey, { data, timestamp: Date.now() });
+  // Clean up old entries periodically
+  if (historyCache.size > 100) {
+    const now = Date.now();
+    for (const [key, value] of historyCache) {
+      if (now - value.timestamp > HISTORY_CACHE_TTL) {
+        historyCache.delete(key);
+      }
+    }
+  }
+}
+
 // Allowed file types
 const ALLOWED_TYPES = {
   // Images
@@ -99,6 +125,19 @@ const upload = multer({
   }
 });
 
+// Cleanup uploads for a session
+function cleanupSessionUploads(sessionId) {
+  try {
+    const sessionDir = join(UPLOAD_DIR, sessionId);
+    if (existsSync(sessionDir)) {
+      rmSync(sessionDir, { recursive: true, force: true });
+      console.log(`[Cleanup] Removed upload directory for session: ${sessionId}`);
+    }
+  } catch (err) {
+    console.error(`[Cleanup] Failed to remove uploads for session ${sessionId}:`, err.message);
+  }
+}
+
 // Load hosts configuration
 const CONFIG_PATH = process.env.CONFIG_PATH || '/app/config/hosts.json';
 let hostsConfig = { hosts: {}, defaults: { scanSubdirs: true, maxDepth: 1 } };
@@ -181,6 +220,8 @@ setInterval(() => {
         }
       }
       sessions.delete(id);
+      // Also cleanup uploads
+      cleanupSessionUploads(id);
     }
   }
 }, 60 * 60 * 1000);  // Check hourly
@@ -548,6 +589,14 @@ app.get('/api/history/:project', requireAuth, async (req, res) => {
     const isSSH = host?.connection?.type === 'ssh';
     console.log(`[History] Resolved - projectPath: ${projectPath}, hostId: ${hostId}, isSSH: ${isSSH}`);
 
+    // Check cache first
+    const cacheKey = `${hostId || 'local'}:${projectPath}`;
+    const cached = getCachedHistory(cacheKey);
+    if (cached) {
+      console.log(`[History] Cache hit for ${cacheKey}`);
+      return res.json(cached);
+    }
+
     // Convert project path to Claude's folder naming convention
     const projectFolder = projectPath.replace(/\//g, '-');
 
@@ -581,9 +630,11 @@ app.get('/api/history/:project', requireAuth, async (req, res) => {
 
         const sessionId = basename(latestFile).replace('.jsonl', '');
         const messages = parseHistoryContent(content);
+        const result = { messages, sessionId, source: 'ssh' };
 
         console.log(`[History] SSH - Returning ${messages.length} messages from session ${sessionId}`);
-        return res.json({ messages, sessionId, source: 'ssh' });
+        setCachedHistory(cacheKey, result);
+        return res.json(result);
       } catch (sshErr) {
         console.error('SSH history fetch error:', sshErr.message);
         return res.json({ messages: [], sessionId: null, error: sshErr.message });
@@ -617,8 +668,10 @@ app.get('/api/history/:project', requireAuth, async (req, res) => {
     const sessionId = latestFile.name.replace('.jsonl', '');
     const content = readFileSync(latestFile.path, 'utf-8');
     const messages = parseHistoryContent(content);
+    const result = { messages, sessionId };
 
-    res.json({ messages, sessionId });
+    setCachedHistory(cacheKey, result);
+    res.json(result);
   } catch (err) {
     console.error('Error reading history:', err);
     res.status(500).json({ error: err.message });
@@ -1342,6 +1395,8 @@ wss.on('connection', async (ws, req) => {
       claudeProcess.kill();
       sessions.delete(sessionId);
     }
+    // Cleanup uploaded files for this session
+    cleanupSessionUploads(sessionId);
   });
 
   ws.on('error', (err) => {