Add native self-hosted instance connection to fluxer_desktop

Trimmed monorepo checkout (fluxer_desktop + packages/voice_engine_v2 +
tools/ci) with a "Connect to a Different Server" menu item and popout
that lets the desktop app switch to any self-hosted Fluxer instance,
plus fixes for well-known discovery on single-domain self-hosted
deployments and a false-positive ERR_ABORTED on same-origin client
redirects during the switch. Defaults to chat.fluxr.chat and uses an
isolated userData directory from the official build.

fluxer_desktop/native/encoder-ring/benches/baseline.json

@@ -0,0 +1,25 @@
+{
+	"measured_at": "85e057a273fd",
+	"host": "darwin-arm64-apple-silicon",
+	"regression_budget_percent": 5.0,
+	"criterion_args": {
+		"warm_up_time_sec": 2,
+		"measurement_time_sec": 5
+	},
+	"benches": {
+		"encoder_input_ring/submit_poll_release_1080p_nv12": {
+			"median_ns": 16.806,
+			"low_ns": 16.663,
+			"high_ns": 16.951,
+			"budget_percent_override": 10.0,
+			"note": "~17ns hot loop; same noise-floor reasoning as other sub-50ns benches."
+		},
+		"encoder_input_ring/submit_then_drain_eight_1080p_nv12": {
+			"median_ns": 112590.0,
+			"low_ns": 108530.0,
+			"high_ns": 117050.0,
+			"budget_percent_override": 10.0,
+			"note": "8x submit + 8x drain. Allocator-touchy; observed cross-run sigma ~5-7% on a loaded host."
+		}
+	}
+}