v0.14.0: Per-drive backup architecture + storage path overhaul

Major refactor of backup and storage paths:

- Per-drive restic repos at <drive>/backups/primary/restic/
- Per-app DB dumps at <drive>/backups/primary/<app>/db-dumps/
- Remove global BackupDir, DBDumpDir, ResticRepo config fields
- Add SystemDataPath config (fallback for apps without HDD)
- New backup/paths.go with pure path computation helpers
- Add GetStackHDDPath to StackDataProvider interface
- Restic methods now accept repoPath as parameter
- Cross-drive backup uses new secondary path structure
- Rename storage/ to appdata/ in scripts and compose templates
- Update protected HDD paths (storage → appdata + backups)
- Simplify backup UI (remove global path displays)

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

controller/internal/config/config.go

@@ -46,11 +46,10 @@ type InfrastructureConfig struct {
 }
 
 type PathsConfig struct {
-	StacksDir string `yaml:"stacks_dir"`
-	DataDir   string `yaml:"data_dir"`
-	BackupDir string `yaml:"backup_dir"`
-	DBDumpDir string `yaml:"db_dump_dir"`
-	HDDPath   string `yaml:"hdd_path"`
+	StacksDir      string `yaml:"stacks_dir"`
+	DataDir        string `yaml:"data_dir"`
+	SystemDataPath string `yaml:"system_data_path"`
+	HDDPath        string `yaml:"hdd_path"`
 }
 
 type WebConfig struct {
@@ -75,7 +74,6 @@ type StacksConfig struct {
 
 type BackupConfig struct {
 	Enabled            bool            `yaml:"enabled"`
-	ResticRepo         string          `yaml:"restic_repo"`
 	ResticPasswordFile string          `yaml:"restic_password_file"`
 	DBDumpSchedule     string          `yaml:"db_dump_schedule"`
 	ResticSchedule     string          `yaml:"restic_schedule"`
@@ -185,13 +183,11 @@ func applyDefaults(cfg *Config) {
 
 	d(&cfg.Paths.StacksDir, "/opt/docker/stacks")
 	d(&cfg.Paths.DataDir, "/opt/docker/felhom-controller/data")
-	d(&cfg.Paths.BackupDir, "/srv/backups")
-	d(&cfg.Paths.DBDumpDir, "/srv/backups/db-dumps")
+	d(&cfg.Paths.SystemDataPath, "/mnt/sys_drive")
 	d(&cfg.Web.Listen, ":8080")
 	d(&cfg.Git.Branch, "main")
 	d(&cfg.Git.SyncInterval, "15m")
 	d(&cfg.Stacks.UpdateWindow, "03:00-05:00")
-	d(&cfg.Backup.ResticRepo, "/srv/backups/restic-repo")
 	d(&cfg.Backup.DBDumpSchedule, "02:30")
 	d(&cfg.Backup.ResticSchedule, "03:00")
 	d(&cfg.Backup.PruneSchedule, "weekly")