Bump version to 1.0.11

Machine status probe on page load:
- POST /api/machines/refresh probes all machines in parallel (max 20 concurrent, 1.5s timeout)
- Updates DB status and broadcasts via SSE to all connected browser tabs
- Server-side throttle: ignores refresh requests within 10s
- Machines.tsx and Dashboard.tsx fire probe on mount
- Visual "Checking machine status..." indicator in Machines table
- MachineHandler now accepts *Engine for ProbeAllMachines access

Makefile

@@ -1,5 +1,5 @@
 BINARY=syncserver
-VERSION?=1.0.10
+VERSION?=1.0.11
 GO?=go
 LDFLAGS=-s -w -X main.version=$(VERSION) -X main.commit=$(shell git rev-parse --short HEAD 2>/dev/null || echo unknown)
 BUILD_FLAGS=CGO_ENABLED=0