feat(backend): add standalone data plane

Replace the Supabase application data plane with the Node/PostgreSQL API, migrate mobile, admin, web, and MCP callers, add controlled cutover tooling, and define hardened Dokploy infrastructure.

apps/mobile/src/lib/authClient.ts

@@ -0,0 +1,67 @@
+import "react-native-url-polyfill/auto";
+import AsyncStorage from "@react-native-async-storage/async-storage";
+import { createClient } from "@supabase/supabase-js";
+import { Platform } from "react-native";
+
+// Supabase is retained as Sauci's identity provider only. Product data should
+// Product data uses apiClient. This client is intentionally Auth-only.
+const memoryStorage: Record<string, string> = {};
+
+const ExpoStorageAdapter = {
+    getItem: async (key: string): Promise<string | null> => {
+        if (Platform.OS === "web") {
+            if (typeof window !== "undefined" && typeof window.localStorage !== "undefined") {
+                return window.localStorage.getItem(key);
+            }
+            return memoryStorage[key] ?? null;
+        }
+        return AsyncStorage.getItem(key);
+    },
+    setItem: async (key: string, value: string): Promise<void> => {
+        if (Platform.OS === "web") {
+            if (typeof window !== "undefined" && typeof window.localStorage !== "undefined") {
+                window.localStorage.setItem(key, value);
+                return;
+            }
+            memoryStorage[key] = value;
+            return;
+        }
+        await AsyncStorage.setItem(key, value);
+    },
+    removeItem: async (key: string): Promise<void> => {
+        if (Platform.OS === "web") {
+            if (typeof window !== "undefined" && typeof window.localStorage !== "undefined") {
+                window.localStorage.removeItem(key);
+                return;
+            }
+            delete memoryStorage[key];
+            return;
+        }
+        await AsyncStorage.removeItem(key);
+    },
+};
+
+const supabaseUrl = process.env.EXPO_PUBLIC_SUPABASE_URL;
+const supabaseAnonKey = process.env.EXPO_PUBLIC_SUPABASE_ANON_KEY;
+const isTestEnv = process.env.NODE_ENV === "test" || process.env.JEST_WORKER_ID !== undefined;
+
+if (!isTestEnv && (!supabaseUrl || !supabaseAnonKey)) {
+    const missing = [];
+    if (!supabaseUrl) missing.push("EXPO_PUBLIC_SUPABASE_URL");
+    if (!supabaseAnonKey) missing.push("EXPO_PUBLIC_SUPABASE_ANON_KEY");
+    const message = `Missing required environment variables: ${missing.join(", ")}. App cannot start.`;
+    console.error("[Auth]", message);
+    throw new Error(message);
+}
+
+const finalUrl = supabaseUrl || (isTestEnv ? "https://test.supabase.co" : "");
+const finalKey = supabaseAnonKey || (isTestEnv ? "test-key" : "");
+
+export const authClient = createClient(finalUrl, finalKey, {
+    auth: {
+        storage: ExpoStorageAdapter,
+        autoRefreshToken: true,
+        persistSession: true,
+        detectSessionInUrl: Platform.OS === "web",
+    },
+});