Architecture change to modules started.

- Added module-interface (module.go).
- Rewritten main function, added Registry (main.go)

module.go

@@ -0,0 +1,39 @@
+package main
+
+import (
+	"context"
+	"net/http"
+
+	"github.com/gorilla/mux"
+)
+
+// Module represents a self-contained feature of Varde.
+// Each module is independently enabled/disabled via config and
+// runs in the same process, sharing the HTTP router where relevant.
+type Module interface {
+	// Name returns a short, unique identifier used in logs and config.
+	Name()
+
+	// Enabled reports whether this module should be started
+	// based on the loaded configuration.
+	Enabled(cfg *Config) bool
+
+	// RegisterRoutes attaches this module's HTTP routes to the shared router, if any.
+	// Modules without HTTP routes should leave this empty.
+	RegisterRoutes(r *musx.Router, cfg *Config)
+
+	// Start runs any background work for this module (eg. periodic checks, repo cloning).
+	// Should block until ctx is cancelled, or return immediately if the module has no background work.
+	Start(ctx context.Context, cfg *Config) error
+
+	// Stop performs graceful cleanup. Called druing shutdown for every module that was successfully started.
+	Stop(ctx context.Context) error
+}
+
+// baseModule provides no-op defaults so modules only need to implement the methods relevant to them.
+type baseModule struct{}
+
+func (baseModule) RegisterRoutes(r *mux.Router, cfg *Config){}
+func (baseModule) Start(cxt context.Context, cfg *Config) error {return nil}
+
+var _ = http.MethodGet // placeholder import guard, remove once a module uses net/http directly here