frontend: deep-link via ?instance=; client/frontend default to :9090; Makefile help; v1.1.0

- cmd/frontend/web: honour ?instance=<hostname> query parameter on the
  initial scope hydration so /view/?instance=lb-ams opens the dashboard
  scoped to that maglevd. The cookie is updated on consumption; an
  unknown name still falls back to the first server via App.tsx.

- cmd/client, cmd/frontend: --server now accepts bare hostnames. A new
  internal/netutil.EnsurePort canonicalises addresses by appending
  :9090 when no port is given, with bracketing for bare IPv6 literals.
  Unit test covers the IPv4/IPv6/bracketed/already-ported permutations.

- Makefile: new self-documenting `help` target as the default rule;
  every user-facing target now carries a `## ` description that the
  awk-based help auto-extracts. fixstyle-web skips with a friendly
  message when prettier isn't installed instead of failing on npx.

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

internal/netutil/netutil_test.go

@@ -0,0 +1,35 @@
+// SPDX-License-Identifier: Apache-2.0
+
+package netutil
+
+import "testing"
+
+func TestEnsurePort(t *testing.T) {
+	const dp = "9090"
+	cases := []struct {
+		in, want string
+	}{
+		{"", ""},
+		{"chbtl2", "chbtl2:9090"},
+		{"chbtl2:9090", "chbtl2:9090"},
+		{"chbtl2:1234", "chbtl2:1234"},
+		{"lb-ams.example.com", "lb-ams.example.com:9090"},
+		{"lb-ams.example.com:9090", "lb-ams.example.com:9090"},
+		{"192.0.2.1", "192.0.2.1:9090"},
+		{"192.0.2.1:9090", "192.0.2.1:9090"},
+		{"::1", "[::1]:9090"},
+		{"2001:db8::1", "[2001:db8::1]:9090"},
+		{"[::1]:9090", "[::1]:9090"},
+		{"[2001:db8::1]:443", "[2001:db8::1]:443"},
+		// Already-bracketed but missing port: net.SplitHostPort rejects
+		// it, ParseIP rejects the bracketed textual form, so the plain
+		// concat path adds ":9090" and yields a valid host:port.
+		{"[::1]", "[::1]:9090"},
+	}
+	for _, tc := range cases {
+		got := EnsurePort(tc.in, dp)
+		if got != tc.want {
+			t.Errorf("EnsurePort(%q) = %q, want %q", tc.in, got, tc.want)
+		}
+	}
+}