v0.6.0: healthcheck + hub reporting implementation

- Add heartbeat ping (every 5 min, controller alive signal)
- Add backup integrity check (weekly restic check, Sunday 04:00)
- Add Heartbeat + BackupIntegrity fields to PingUUIDsConfig
- Add HubConfig for central hub reporting
- Add report package (types, builder, pusher) for hub push
- Wire hub reporting into scheduler (configurable interval)
- Update controller.yaml.example with new monitoring + hub sections
- Add monitoring/DEPRECATED.md for legacy bash scripts

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

controller/internal/report/pusher.go

@@ -0,0 +1,86 @@
+package report
+
+import (
+	"bytes"
+	"encoding/json"
+	"fmt"
+	"io"
+	"log"
+	"net/http"
+	"strings"
+	"time"
+
+	"gitea.dooplex.hu/admin/felhom-controller/internal/config"
+)
+
+// Pusher sends reports to the central hub.
+type Pusher struct {
+	hubURL     string
+	apiKey     string
+	httpClient *http.Client
+	logger     *log.Logger
+	enabled    bool
+}
+
+// NewPusher creates a new report pusher from hub configuration.
+func NewPusher(cfg *config.HubConfig, logger *log.Logger) *Pusher {
+	return &Pusher{
+		hubURL: strings.TrimRight(cfg.URL, "/"),
+		apiKey: cfg.APIKey,
+		httpClient: &http.Client{
+			Timeout: 30 * time.Second,
+		},
+		logger:  logger,
+		enabled: cfg.Enabled,
+	}
+}
+
+// Push sends a report to the hub. Retries 3 times with 5s backoff.
+// Never returns error to caller — push failures should not affect controller operation.
+func (p *Pusher) Push(report *Report) error {
+	if !p.enabled {
+		return nil
+	}
+
+	data, err := json.Marshal(report)
+	if err != nil {
+		p.logger.Printf("[WARN] Hub report marshal failed: %v", err)
+		return nil
+	}
+
+	url := p.hubURL + "/api/v1/report"
+
+	var lastErr error
+	for attempt := 0; attempt < 3; attempt++ {
+		if attempt > 0 {
+			time.Sleep(5 * time.Second)
+		}
+
+		req, err := http.NewRequest(http.MethodPost, url, bytes.NewReader(data))
+		if err != nil {
+			lastErr = err
+			continue
+		}
+		req.Header.Set("Content-Type", "application/json")
+		if p.apiKey != "" {
+			req.Header.Set("Authorization", "Bearer "+p.apiKey)
+		}
+
+		resp, err := p.httpClient.Do(req)
+		if err != nil {
+			lastErr = err
+			continue
+		}
+		io.Copy(io.Discard, resp.Body)
+		resp.Body.Close()
+
+		if resp.StatusCode >= 200 && resp.StatusCode < 300 {
+			p.logger.Printf("[INFO] Hub report pushed successfully (%d bytes)", len(data))
+			return nil
+		}
+		lastErr = fmt.Errorf("HTTP %d", resp.StatusCode)
+	}
+
+	p.logger.Printf("[WARN] Hub report push failed after 3 attempts: %v", lastErr)
+	return nil
+}