feat(frontend): adapter web HTTP+WebSocket derrière les ports (#13)

Lot F1 du chantier server/client mode : nouvel adaptateur web branché
derrière les ports d'invocation et de flux live, permettant au frontend de
dialoguer avec le backend via HTTP + WebSocket en mode client/serveur. Le
mode desktop (Tauri IPC) reste inchangé.

- frontend/src/adapters/http : invoker HTTP, client live WebSocket, gateways
  request/response et stream, frames, garde unsupported (7 fichiers + 2 tests).
- frontend/src/app : câblage DI (di.tsx) et son test, typage vite-env.d.ts.

Validé : build vert, garde no-direct-invoke verte, 724 tests verts,
desktop inchangé.

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

frontend/src/app/di.tsx

@@ -1,9 +1,10 @@
 /**
  * Dependency-injection provider for the UI ports.
  *
- * Chooses real Tauri adapters vs mocks based on `VITE_USE_MOCK` (any truthy
- * value → mocks). Components consume gateways via {@link useGateways} and never
- * construct adapters or call `invoke()` themselves.
+ * Chooses one of three transport implementations (ticket #13): the mock adapters
+ * (`VITE_USE_MOCK`), the web HTTP+WS adapters (`VITE_TRANSPORT="http"`), or the
+ * default Tauri desktop adapters. Components consume gateways via
+ * {@link useGateways} and never construct adapters or call `invoke()` themselves.
  */
 
 import {
@@ -16,18 +17,45 @@ import {
 import type { Gateways } from "@/ports";
 import { createTauriGateways } from "@/adapters";
 import { createMockGateways } from "@/adapters/mock";
+import { createHttpWsGateways } from "@/adapters/http";
 
 const GatewaysContext = createContext<Gateways | null>(null);
 
+/** The selected transport backing the gateways. */
+export type Transport = "mock" | "http" | "tauri";
+
 /** Whether the mock adapters should be used (env-driven, overridable in tests). */
 export function shouldUseMock(): boolean {
   const flag = import.meta.env.VITE_USE_MOCK;
   return flag === "1" || flag === "true";
 }
 
+/**
+ * Whether the web (client/server) HTTP+WS adapters should be used. Selected
+ * explicitly via `VITE_TRANSPORT="http"` so the desktop path stays the default
+ * and is never affected (ticket #13, lot F1).
+ */
+export function shouldUseHttp(): boolean {
+  return import.meta.env.VITE_TRANSPORT === "http";
+}
+
+/** Resolves which transport to use. Mock wins, then explicit web, else Tauri. */
+export function resolveTransport(): Transport {
+  if (shouldUseMock()) return "mock";
+  if (shouldUseHttp()) return "http";
+  return "tauri";
+}
+
 /** Resolves the gateway set for the current environment. */
 export function resolveGateways(): Gateways {
-  return shouldUseMock() ? createMockGateways() : createTauriGateways();
+  switch (resolveTransport()) {
+    case "mock":
+      return createMockGateways();
+    case "http":
+      return createHttpWsGateways();
+    case "tauri":
+      return createTauriGateways();
+  }
 }
 
 interface DIProviderProps {