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/attach.go

@@ -1,13 +1,17 @@
 package storage
 
+import "log"
+
 // AttachRequest holds parameters for attaching an existing partition
 // without formatting — using a bind mount from a subfolder.
 type AttachRequest struct {
-	DevicePath string // "/dev/sdb1" — must have an existing filesystem
-	MountName  string // "hdd_1" → bind-mounts at /mnt/hdd_1
-	SubPath    string // full path on raw mount to bind-mount (e.g., "/mnt/.felhom-raw/hdd_1/felhom_data")
-	Label      string // Display label for the UI
-	SetDefault bool   // Register as default storage path
+	DevicePath string      // "/dev/sdb1" — must have an existing filesystem
+	MountName  string      // "hdd_1" → bind-mounts at /mnt/hdd_1
+	SubPath    string      // full path on raw mount to bind-mount (e.g., "/mnt/.felhom-raw/hdd_1/felhom_data")
+	Label      string      // Display label for the UI
+	SetDefault bool        // Register as default storage path
+	Logger     *log.Logger // Optional logger for debug output
+	Debug      bool        // Enable debug logging
 }
 
 // DirEntry represents a directory entry returned by ListDirectories.