server: drop in-process TLS — HTTP-only behind reverse proxy

Self-hosted deployments already terminate TLS at Caddy/Traefik/nginx;
making the server do TLS too means double cert config, dual ACME
plumbing, and an untested code path. Drop RM_TLS_CERT/RM_TLS_KEY,
remove TLSEnabled() and the ListenAndServeTLS branch.

Replace the cookie's "Secure if TLS-in-process" check with a new
RM_COOKIE_SECURE flag (default true). Local HTTP-only testing sets
RM_COOKIE_SECURE=false; production is always behind a TLS proxy and
the cookie stays Secure.

Default port :8443 → :8080. docker-compose binds 127.0.0.1 only and
populates RM_TRUSTED_PROXY. spec.md §4.1/§10.1 rewritten with a
Caddyfile snippet and a hard "do not expose RM_LISTEN publicly"
warning. enrollResponse keeps cert_pin_sha256 in the shape but the
server can't introspect a cert it doesn't terminate — operator
pastes the proxy's hash into -cert-pin at install time.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

internal/server/http/server.go

@@ -86,6 +86,9 @@ func (s *Server) routes(r chi.Router) {
 
 		// Run-now: dispatch a job to a host's agent.
 		r.Post("/hosts/{id}/jobs", s.handleRunNow)
+
+		// Snapshot projection (refreshed by the agent after each backup).
+		r.Get("/hosts/{id}/snapshots", s.handleListHostSnapshots)
 	})
 
 	// Agent ↔ server WebSocket. Bearer-authenticated inside the handler.
@@ -109,16 +112,9 @@ func (s *Server) routes(r chi.Router) {
 }
 
 // Start begins listening. Blocks until ListenAndServe returns
-// (typically only on Shutdown). Pass the result to errgroup.Group.Go.
+// (typically only on Shutdown). The server is HTTP-only by design;
+// production deployments terminate TLS at a reverse proxy in front.
 func (s *Server) Start() error {
-	cfg := s.deps.Cfg
-	if cfg.TLSEnabled() {
-		err := s.srv.ListenAndServeTLS(cfg.TLSCert, cfg.TLSKey)
-		if errors.Is(err, stdhttp.ErrServerClosed) {
-			return nil
-		}
-		return err
-	}
 	err := s.srv.ListenAndServe()
 	if errors.Is(err, stdhttp.ErrServerClosed) {
 		return nil