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/linux-screen-capture/benches/baseline.json

@@ -0,0 +1,29 @@
+{
+	"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": {
+		"linux_screen_capture/pool_acquire_release/1080p_nv12": {
+			"median_ns": 14.252,
+			"low_ns": 14.201,
+			"high_ns": 14.316,
+			"budget_percent_override": 10.0,
+			"note": "~14ns hot loop; noise floor reasoning."
+		},
+		"linux_screen_capture/simulated_callback/1080p_nv12_copy": {
+			"median_ns": 36690.0,
+			"low_ns": 36375.0,
+			"high_ns": 37029.0
+		},
+		"linux_screen_capture/legacy_baseline/1080p_nv12_vec_clone": {
+			"median_ns": 36918.0,
+			"low_ns": 36634.0,
+			"high_ns": 37213.0,
+			"note": "Reference point: prior Vec::clone path that the pool was added to replace. Tracked so that any regression of the pool path back to clone cost is visible."
+		}
+	}
+}