fix: replace frontend with Rust OPAQUE API + Flutter keypad UI

- Full OPAQUE auth flow via WASM client SDK (client-wasm crate)
- New user: Key Register → Key Login → Code Register (icon selection) → done
- Existing user: Key Login → get login-data → icon keypad → Code Login → done
- Icon-based keypad matching Flutter design:
  - 2 cols portrait, 3 cols landscape
  - Key tiles with 3-col sub-grid of icons
  - Navy border press feedback
  - Dot display with backspace + submit
- SVGs rendered as-is (no color manipulation)
- SusiPage with Login/Signup tabs
- LoginKeypadPage and SignupKeypadPage for code flows
- Secret key display/copy on signup
- Unit tests for Keypad component
- WASM pkg bundled locally (no external dep)

src/types/index.ts

@@ -0,0 +1,36 @@
+/** Auth state stored in localStorage */
+export interface AuthState {
+  email: string | null
+  secretKeyHex: string | null
+  userId: string | null
+}
+
+/** Icon from the WASM client */
+export interface NKodeIcon {
+  file_name: string
+  file_type: string
+  img_data: string
+}
+
+/** Response from prepareCodeRegistration */
+export interface IconsResponse {
+  icons: NKodeIcon[]
+}
+
+/** Response from prepareCodeLogin */
+export interface CodeLoginData {
+  keypadIndices: number[]
+  propertiesPerKey: number
+  numberOfKeys: number
+  mask: number[]
+  icons: NKodeIcon[]
+  loginDataJson: string
+}
+
+/** Session returned from loginKey / loginCode */
+export interface NKodeSession {
+  sessionId: string
+  userId: string
+  createdAt: string
+  expiresAt: string
+}

src/types/nkode-client-wasm.d.ts

@@ -1,19 +0,0 @@
-/**
- * Type stub for the nKode WASM package.
- * Will be replaced by real types when the package is linked via `bun link`.
- */
-declare module 'nkode-client-wasm' {
-  export class NKodeClient {
-    constructor(base_url: string);
-    loginCode(email: string, passcode_bytes: Uint8Array): Promise<any>;
-    loginKey(email: string, secret_key_hex: string): Promise<any>;
-    registerCode(email: string, passcode_bytes: Uint8Array): Promise<void>;
-    registerKey(email: string, secret_key_hex: string): Promise<void>;
-    static generateSecretKey(): string;
-    free(): void;
-  }
-
-  export function init(): void;
-
-  export default function __wbg_init(module_or_path?: any): Promise<any>;
-}