v0.5.0: Backup bugfixes + monitoring page with metrics store

- Fix "Helyi mentés" showing "–" after controller restart by synthesizing
  LastBackup from snapshot history and LastDBDump from dump files on disk
- New monitoring page (/monitoring) with system info, metrics charts, and
  container resource overview
- SQLite metrics store (modernc.org/sqlite, pure Go, no CGO) with 60s
  collection interval and 30-day auto-prune
- REST API endpoints: /api/metrics/system, /api/metrics/containers/summary,
  /api/metrics/containers/{name}, /api/metrics/sysinfo
- Chart.js 4.4.7 embedded locally for offline environments
- System info provider reads hostname, OS, kernel, CPU, uptime from /proc
- Docker compose updated with /etc/os-release host mount

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

controller/internal/metrics/sysinfo.go

@@ -0,0 +1,110 @@
+//go:build linux
+
+package metrics
+
+import (
+	"bufio"
+	"fmt"
+	"os"
+	"runtime"
+	"strings"
+	"time"
+)
+
+// GetStaticInfo reads host-level static system information.
+// Reads from /proc and /etc (which reflect the host in Docker containers).
+func GetStaticInfo() StaticSystemInfo {
+	info := StaticSystemInfo{}
+
+	// Hostname
+	info.Hostname, _ = os.Hostname()
+
+	// OS — try host mount first, fall back to container's
+	info.OS = readOSRelease("/host/etc/os-release")
+	if info.OS == "" {
+		info.OS = readOSRelease("/etc/os-release")
+	}
+
+	// Kernel version
+	if data, err := os.ReadFile("/proc/sys/kernel/osrelease"); err == nil {
+		info.Kernel = strings.TrimSpace(string(data))
+	}
+
+	// Architecture
+	if data, err := os.ReadFile("/proc/sys/kernel/arch"); err == nil {
+		info.Architecture = strings.TrimSpace(string(data))
+	}
+	if info.Architecture == "" {
+		// Fallback: use uname -m equivalent from /proc/cpuinfo or runtime
+		info.Architecture = runtime.GOARCH
+		// Try to get the actual host arch
+		if data, err := os.ReadFile("/proc/version"); err == nil {
+			v := string(data)
+			if strings.Contains(v, "x86_64") {
+				info.Architecture = "x86_64"
+			} else if strings.Contains(v, "aarch64") {
+				info.Architecture = "aarch64"
+			}
+		}
+	}
+
+	// CPU model and cores
+	info.CPUModel, info.CPUCores = readCPUInfo()
+	if info.CPUCores == 0 {
+		info.CPUCores = runtime.NumCPU()
+	}
+
+	// Uptime
+	if data, err := os.ReadFile("/proc/uptime"); err == nil {
+		var uptimeSec float64
+		if _, err := fmt.Sscanf(string(data), "%f", &uptimeSec); err == nil {
+			info.UptimeSeconds = int64(uptimeSec)
+			info.BootTime = time.Now().Add(-time.Duration(info.UptimeSeconds) * time.Second)
+		}
+	}
+
+	return info
+}
+
+// readOSRelease reads PRETTY_NAME from an os-release file.
+func readOSRelease(path string) string {
+	f, err := os.Open(path)
+	if err != nil {
+		return ""
+	}
+	defer f.Close()
+
+	scanner := bufio.NewScanner(f)
+	for scanner.Scan() {
+		line := scanner.Text()
+		if strings.HasPrefix(line, "PRETTY_NAME=") {
+			val := strings.TrimPrefix(line, "PRETTY_NAME=")
+			val = strings.Trim(val, `"`)
+			return val
+		}
+	}
+	return ""
+}
+
+// readCPUInfo reads the CPU model name and number of cores from /proc/cpuinfo.
+func readCPUInfo() (model string, cores int) {
+	f, err := os.Open("/proc/cpuinfo")
+	if err != nil {
+		return "", 0
+	}
+	defer f.Close()
+
+	scanner := bufio.NewScanner(f)
+	for scanner.Scan() {
+		line := scanner.Text()
+		if strings.HasPrefix(line, "model name") {
+			if idx := strings.Index(line, ":"); idx >= 0 {
+				model = strings.TrimSpace(line[idx+1:])
+			}
+		}
+		if strings.HasPrefix(line, "processor") {
+			cores++
+		}
+	}
+	return model, cores
+}