Add SSH source support with dialstdio and UI components

- Implement SSH dial via stdio for remote connections
- Add sources API and storage layer for managing connection sources
- Add SourcePanel and SshFields web components for SSH configuration
- Update app structure to support source-based connections
- Update handlers and server for new sources endpoint

Co-Authored-By: Claude Haiku 4.5 <noreply@anthropic.com>

internal/api/server.go

@@ -11,9 +11,9 @@ import (
 	"os"
 	"path/filepath"
 	"strings"
+	"sync"
 	"time"
 
-	"github.com/arescom/dockmv/internal/dkr"
 	"github.com/arescom/dockmv/internal/job"
 	"github.com/arescom/dockmv/internal/sshx"
 	"github.com/arescom/dockmv/internal/store"
@@ -29,23 +29,31 @@ type Config struct {
 	DataDir string
 	// PackageDir is where migration packages are written.
 	PackageDir string
-	// DockerHost overrides the source daemon address.
+	// DockerHost overrides the local source daemon address.
 	DockerHost string
+	// DockerHostSet reports that DockerHost was given explicitly on the command
+	// line. It then wins over the source remembered from the last run.
+	DockerHostSet bool
 	// UI is the embedded web app; nil disables the UI.
 	UI fs.FS
 	// Logger receives request and error logs.
 	Logger *slog.Logger
 }
 
-// Server ties the Docker client, connection store and job manager to HTTP.
+// Server ties the source daemon, connection store and job manager to HTTP.
 type Server struct {
-	cfg    Config
-	log    *slog.Logger
-	docker *dkr.Client
-	conns  *store.Connections
-	hosts  *sshx.KnownHosts
-	jobs   *job.Manager
-	mux    *http.ServeMux
+	cfg     Config
+	log     *slog.Logger
+	sources *store.Sources
+	conns   *store.Connections
+	hosts   *sshx.KnownHosts
+	jobs    *job.Manager
+	mux     *http.ServeMux
+
+	// srcMu guards cur, the connection to the selected source. It is opened on
+	// first use and replaced when the operator picks another source.
+	srcMu sync.Mutex
+	cur   *sourceConn
 }
 
 // New builds the server and everything it owns.
@@ -60,10 +68,6 @@ func New(cfg Config) (*Server, error) {
 		return nil, fmt.Errorf("create package directory: %w", err)
 	}
 
-	docker, err := dkr.New(cfg.DockerHost)
-	if err != nil {
-		return nil, err
-	}
 	conns, err := store.NewConnections(filepath.Join(cfg.DataDir, "connections.json"))
 	if err != nil {
 		return nil, err
@@ -72,17 +76,35 @@ func New(cfg Config) (*Server, error) {
 	if err != nil {
 		return nil, err
 	}
+	local := store.Source{Name: "this host", DockerHost: cfg.DockerHost}
+	if local.DockerHost == "" {
+		local.DockerHost = os.Getenv("DOCKER_HOST")
+	}
+	sources, err := store.NewSources(filepath.Join(cfg.DataDir, "sources.json"), local)
+	if err != nil {
+		return nil, err
+	}
+	// An explicit --docker-host is an instruction for this run, so it overrides
+	// the source remembered from the last one.
+	if cfg.DockerHostSet {
+		if err := sources.Select(store.LocalSourceID); err != nil {
+			return nil, err
+		}
+	}
 
 	s := &Server{
-		cfg: cfg, log: cfg.Logger, docker: docker,
+		cfg: cfg, log: cfg.Logger, sources: sources,
 		conns: conns, hosts: hosts, jobs: job.NewManager(), mux: http.NewServeMux(),
 	}
 	s.routes()
 	return s, nil
 }
 
-// Close releases the Docker connection.
-func (s *Server) Close() error { return s.docker.Close() }
+// Close releases the connection to the current source.
+func (s *Server) Close() error {
+	s.invalidateSource("")
+	return nil
+}
 
 // Handler returns the root HTTP handler.
 func (s *Server) Handler() http.Handler {
@@ -96,6 +118,13 @@ func (s *Server) routes() {
 	m.HandleFunc("GET /api/source", s.handleSource)
 	m.HandleFunc("GET /api/source/sizes", s.handleSourceSizes)
 
+	m.HandleFunc("GET /api/sources", s.handleListSources)
+	m.HandleFunc("POST /api/sources", s.handleSaveSource)
+	m.HandleFunc("DELETE /api/sources/{id}", s.handleDeleteSource)
+	m.HandleFunc("POST /api/sources/{id}/select", s.handleSelectSource)
+	m.HandleFunc("POST /api/sources/{id}/probe", s.handleSourceProbe)
+	m.HandleFunc("POST /api/sources/{id}/trust", s.handleSourceTrust)
+
 	m.HandleFunc("GET /api/connections", s.handleListConnections)
 	m.HandleFunc("POST /api/connections", s.handleSaveConnection)
 	m.HandleFunc("DELETE /api/connections/{id}", s.handleDeleteConnection)