fix: P0+P1 critical bug fixes across controller (24 files)

Concurrency fixes:
- Deep-copy stacks in GetStack/GetStacks to prevent shared state mutation (C04)
- Add per-state mutex to watchdog pathProbeState (C05)
- Guard MetricsCollector.Start() with sync.Once against double-start (C06)
- Hold diskJobMu across entire raw mount operation (C07)
- Add mutex to SetEncryptionKey (C08), MigrateEncryption write lock (H03)
- Use sync.Once for sync.Stop() channel close (H08)
- Set syncing=true before releasing lock in TriggerSync (H09)
- Deep-copy lastDBDump/lastBackup in GetFullStatus (H11)
- Add WaitGroup for stderr goroutine in MigrateDrive (H19)
- Add mutex to SetBackupRunningCheck (M18)

Security fixes:
- Validate Bearer token against Hub API key in CSRF middleware (H16)
- Validate backup paths start with expected prefix in RemoveStack (M12)
- Guard uuid[:8] slice with length check (H20)
- Parse fstab fields exactly for mount target matching (H21)

Bug fixes:
- Use decrypted env vars for compose deploy (C01)
- Log decrypt failures in DecryptMap instead of swallowing (C02)
- Move Deployed=false inside lock in runComposeDeploy (C03)
- Fix activeDrives() to skip disconnected drives (H02)
- Fix Snapshot() stderr extraction from exec.ExitError (H01)
- Check unlockCmd.Run() error in restic (H01)
- Buffer template rendering via bytes.Buffer (H07)
- Thread context.Context through cloudflare client (H10)
- Fix leaf-name collision detection in cross-drive backup (H15)
- Add nil check for crossDriveRunner (H17)
- Use strings.TrimSpace instead of slice on command output (H18)
- Make SaveAppConfig atomic with write-to-tmp+rename (H04)
- Pass encKey on deploy failure SaveAppConfig (H05)
- Fix IPv6 address format in TCP health probe

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

controller/internal/stacks/manager.go

@@ -112,6 +112,8 @@ func NewManager(cfg *config.Config, logger *log.Logger) (*Manager, error) {
 
 // SetEncryptionKey sets the AES-256 key used to encrypt/decrypt sensitive values in app.yaml.
 func (m *Manager) SetEncryptionKey(key []byte) {
+	m.mu.Lock()
+	defer m.mu.Unlock()
 	m.encKey = key
 }
 
@@ -121,8 +123,8 @@ func (m *Manager) MigrateEncryption() {
 	if m.encKey == nil {
 		return
 	}
-	m.mu.RLock()
-	defer m.mu.RUnlock()
+	m.mu.Lock()
+	defer m.mu.Unlock()
 
 	migrated := 0
 	for _, s := range m.stacks {
@@ -446,7 +448,7 @@ func (m *Manager) GetStacks() []Stack {
 
 	result := make([]Stack, 0, len(m.stacks))
 	for _, s := range m.stacks {
-		result = append(result, *s)
+		result = append(result, deepCopyStack(s))
 	}
 
 	// Sort alphabetically by display name for consistent UI ordering
@@ -465,8 +467,53 @@ func (m *Manager) GetStack(name string) (*Stack, bool) {
 	if !ok {
 		return nil, false
 	}
-	copy := *s
-	return &copy, true
+	cp := deepCopyStack(s)
+	return &cp, true
+}
+
+// deepCopyStack creates a deep copy of a Stack, including pointer fields.
+func deepCopyStack(s *Stack) Stack {
+	cp := *s
+
+	// Deep-copy Containers slice
+	if s.Containers != nil {
+		cp.Containers = make([]ContainerInfo, len(s.Containers))
+		copy(cp.Containers, s.Containers)
+	}
+
+	// Deep-copy AppConfig pointer
+	if s.AppConfig != nil {
+		acCopy := *s.AppConfig
+		if s.AppConfig.Env != nil {
+			acCopy.Env = make(map[string]string, len(s.AppConfig.Env))
+			for k, v := range s.AppConfig.Env {
+				acCopy.Env[k] = v
+			}
+		}
+		if s.AppConfig.LockedFields != nil {
+			acCopy.LockedFields = make([]string, len(s.AppConfig.LockedFields))
+			copy(acCopy.LockedFields, s.AppConfig.LockedFields)
+		}
+		cp.AppConfig = &acCopy
+	}
+
+	// Deep-copy HealthProbe pointer
+	if s.HealthProbe != nil {
+		hpCopy := *s.HealthProbe
+		if s.HealthProbe.Details != nil {
+			hpCopy.Details = make([]HealthCheckDetail, len(s.HealthProbe.Details))
+			copy(hpCopy.Details, s.HealthProbe.Details)
+		}
+		cp.HealthProbe = &hpCopy
+	}
+
+	// Deep-copy Meta.DeployFields slice
+	if s.Meta.DeployFields != nil {
+		cp.Meta.DeployFields = make([]DeployField, len(s.Meta.DeployFields))
+		copy(cp.Meta.DeployFields, s.Meta.DeployFields)
+	}
+
+	return cp
 }
 
 // --- Stack operations ---