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/nv12-gpu-pack/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": {
+		"nv12_pack_1080p_cache_hit": {
+			"median_ns": 1517400.0,
+			"low_ns": 1492800.0,
+			"high_ns": 1542000.0,
+			"budget_percent_override": 20.0,
+			"note": "Requires a wgpu adapter (Metal on macOS). Bench function returns early without an adapter. GPU jobs are noisy; cross-run sigma 10-15% on a loaded host."
+		},
+		"nv12_pack_1080p_cache_miss": {
+			"median_ns": 3081300.0,
+			"low_ns": 3026300.0,
+			"high_ns": 3139400.0,
+			"budget_percent_override": 20.0,
+			"note": "Wgpu adapter required; same caveat as cache_hit."
+		}
+	}
+}