fix: disk explosion prevention + auth leak fix + health endpoint routing

- health-checker.js: Strip response headers from history, cap at 500 entries per service, compact JSON save
- resource-monitor.js: Cap at 500 entries per container, compact JSON save
- middleware.js: Block sensitive API routes from external access when TOTP disabled
- Caddyfile: Add health probe routes (/healthz, /readyz, /csrf-token) before SPA fallback
- MCP bridge: Fix internal IP leak in .well-known/mcp.json

Found during comprehensive QA audit of test.dashcaddy.net.

dashcaddy-api/src/monitoring/health-checker.js

@@ -30,6 +30,7 @@ const LEGACY_HEALTH_CONFIG_FILE = path.join(__dirname, 'health-config.json');
 const LEGACY_HEALTH_HISTORY_FILE = path.join(__dirname, 'health-history.json');
 const CHECK_INTERVAL = parseInt(process.env.HEALTH_CHECK_INTERVAL || '30000', 10); // 30 seconds
 const MAX_CHECK_INTERVAL = parseInt(process.env.HEALTH_CHECK_MAX_INTERVAL || '300000', 10); // 5 minutes max backoff
+const MAX_ENTRIES_PER_SERVICE = parseInt(process.env.HEALTH_MAX_ENTRIES || '500', 10); // Cap to prevent disk explosion
 const HISTORY_RETENTION_DAYS = parseInt(process.env.HEALTH_HISTORY_RETENTION || '30', 10);
 
 class HealthChecker extends EventEmitter {
@@ -217,7 +218,7 @@ class HealthChecker extends EventEmitter {
             statusCode: res.statusCode,
             message: healthy ? 'Service is healthy' : 'Service check failed',
             details: {
-              headers: res.headers,
+              headers: res.headers ? { server: res.headers.server } : undefined,  // Compact: disk explosion fix
               bodyLength: data.length
             }
           });
@@ -285,6 +286,11 @@ class HealthChecker extends EventEmitter {
     }
 
     this.history[serviceId].push(status);
+    
+    // Cap entries to prevent unbounded growth (disk explosion fix)
+    if (this.history[serviceId].length > MAX_ENTRIES_PER_SERVICE) {
+      this.history[serviceId] = this.history[serviceId].slice(-MAX_ENTRIES_PER_SERVICE);
+    }
 
     // Emit status event
     this.emit('status-check', status);
@@ -565,6 +571,10 @@ class HealthChecker extends EventEmitter {
       this.history[serviceId] = this.history[serviceId].filter(h =>
         new Date(h.timestamp).getTime() > cutoffTime
       );
+      // Also cap total entries per service
+      if (this.history[serviceId].length > MAX_ENTRIES_PER_SERVICE) {
+        this.history[serviceId] = this.history[serviceId].slice(-MAX_ENTRIES_PER_SERVICE);
+      }
     }
   }
 
@@ -616,7 +626,7 @@ class HealthChecker extends EventEmitter {
    */
   saveHistory() {
     try {
-      fs.writeFileSync(HEALTH_HISTORY_FILE, JSON.stringify(this.history, null, 2));
+      fs.writeFileSync(HEALTH_HISTORY_FILE, JSON.stringify(this.history)); // Compact JSON (no pretty-print) to reduce file size
     } catch (error) {
       this.emit('log', 'error', `Error saving history: ${error.message}`);
     }