fix: standardize log prefixes, remove duplicates, add missing module tags

Second-pass logging cleanup: consistent [LEVEL] [module] format across
all 41 files. Remove stale prefixes ([CF], [SYNC], [SCHED], [API],
[STORAGE], [HEALTH], [ROLLBACK]). Remove 5 duplicate log lines. Gate
ungated DEBUG lines. Fix wrong log levels (restore start WARN→INFO).

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

controller/internal/backup/appdata.go

@@ -3,6 +3,7 @@ package backup
 import (
 	"context"
 	"fmt"
+	"log"
 	"os"
 	"os/exec"
 	"strings"
@@ -105,6 +106,7 @@ func DiscoverAppData(provider StackDataProvider, discoveredDBs []DiscoveredDB) [
 		result = append(result, info)
 	}
 
+	log.Printf("[INFO] [backup] Discovered app data: %d apps", len(result))
 	return result
 }