feat: comprehensive INFO/WARN/ERROR logging across all controller modules

Add structured operational logging at INFO, WARN, and ERROR levels to
every controller module. Standardize custom prefixes ([GEO], [SCHED],
[SYNC]) to use [INFO/WARN/ERROR] [module] format. Fix misleveled logs
(WARN->ERROR for data loss scenarios, WARN->INFO for routine operations).

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

controller/internal/stacks/metadata.go

@@ -1,7 +1,7 @@
 package stacks
 
 import (
-	"fmt"
+	"log"
 	"os"
 	"path/filepath"
 	"strings"
@@ -126,7 +126,7 @@ func LoadMetadata(stackDir string) Metadata {
 	}
 
 	if err := yaml.Unmarshal(data, &meta); err != nil {
-		fmt.Fprintf(os.Stderr, "[ERROR] Failed to parse .felhom.yml in %s: %v\n", stackDir, err)
+		log.Printf("[ERROR] [stacks] Failed to parse .felhom.yml in %s: %v", stackDir, err)
 		dirName := filepath.Base(stackDir)
 		meta.DisplayName = toTitleCase(strings.ReplaceAll(dirName, "-", " "))
 		meta.Slug = dirName