Add boot image management with ISO extraction and serving

Upload Proxmox ISOs via API or dashboard UI, extract kernel+initrd
using pure-Go iso9660 library, store on disk, and serve over HTTP
for PXE booting. Dynamic kernel/initrd filenames per image replace
the previous hardcoded paths.

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

cmd/provisioning/main.go

@@ -16,6 +16,7 @@ import (
 	"provisioning/internal/db"
 	"provisioning/internal/events"
 	"provisioning/internal/httpserver"
+	"provisioning/internal/image"
 	"provisioning/internal/infra"
 	"provisioning/internal/orchestrator"
 	"provisioning/internal/pxe"
@@ -45,11 +46,17 @@ func main() {
 	}
 	defer database.Close()
 
+	if err := os.MkdirAll(cfg.Images.Dir, 0o755); err != nil {
+		log.Fatalf("create images dir: %v", err)
+	}
+
 	hosts := &store.Hosts{DB: database}
 	ops := &store.Operations{DB: database}
 	locks := &store.Locks{DB: database, TTLMinutes: cfg.Locks.TTLMinutes}
 	images := &store.Images{DB: database}
 
+	imageSvc := &image.Service{Store: images, ImageDir: cfg.Images.Dir}
+
 	hub := events.NewHub()
 
 	runner := &orchestrator.Runner{
@@ -91,6 +98,8 @@ func main() {
 		ServerTypes: serverTypes,
 	}
 
+	imageAPI := &api.ImageAPI{Svc: imageSvc}
+
 	hostAPI := &api.HostAPI{
 		Hosts:        hosts,
 		Ops:          ops,
@@ -117,6 +126,7 @@ func main() {
 		Ops:          ops,
 		Locks:        locks,
 		Images:       images,
+		ImageSvc:     imageSvc,
 		Runner:       runner,
 		Orchestrator: hostOrch,
 		Hub:          hub,
@@ -126,10 +136,12 @@ func main() {
 	}
 
 	router := httpserver.NewRouter(httpserver.Deps{
-		HostAPI: hostAPI,
-		BootAPI: bootAPI,
-		UI:      ui,
-		Hub:     hub,
+		HostAPI:  hostAPI,
+		BootAPI:  bootAPI,
+		ImageAPI: imageAPI,
+		UI:       ui,
+		Hub:      hub,
+		ImageDir: cfg.Images.Dir,
 	})
 
 	srv := &http.Server{