v0.24.0 — Pre-testing observability: debug logging, diagnostic dump, startup self-test

- Add [DEBUG] logging across all modules (backup, storage, sync, selfupdate,
  monitor, notify, report, assets, setup) gated behind logging.level: "debug"
- Add /api/debug/dump endpoint returning full controller state JSON (debug only)
- Add startup self-test validating 9 subsystems (Docker, dirs, storage, hub,
  restic repos, metrics DB) with pass/warn/fail summary
- New packages: internal/selftest, internal/util
- Constructor/signature changes: debug bool params, logger params on
  RunHealthCheck and BuildReport, smart watchdog probe logging

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

controller/internal/storage/scan_other.go

@@ -2,9 +2,12 @@
 
 package storage
 
-import "fmt"
+import (
+	"fmt"
+	"log"
+)
 
 // ScanDisks is not supported on non-Linux platforms.
-func ScanDisks() (*ScanResult, error) {
+func ScanDisks(logger *log.Logger, debug bool) (*ScanResult, error) {
 	return nil, fmt.Errorf("storage init is only supported on Linux")
 }