Refactor popup into shared modules, wire up real ERC-20 tokens

Split popup/index.js (784 lines) into focused modules:
- shared/state.js: state management, storage persistence
- shared/wallet.js: mnemonic gen, HD derivation, signing
- shared/prices.js: price cache (5min TTL), USD formatting,
  value aggregation (address → wallet → total)
- shared/balances.js: ETH + ERC-20 balance cache (60s TTL),
  ENS lookup, token contract metadata lookup
- shared/vault.js: unchanged (libsodium encryption)
- shared/tokens.js: unchanged (token list + CoinDesk client)
- popup/index.js: view switching and event wiring only

Token tracking is now app-wide: trackedTokens stored in state,
balances fetched for all tracked tokens across all addresses.
Add Token now calls the real contract to read name/symbol/decimals.
Total portfolio value shown in 2x type on Home screen.

src/shared/state.js

@@ -0,0 +1,49 @@
+// State management and extension storage persistence.
+
+const storageApi =
+    typeof browser !== "undefined"
+        ? browser.storage.local
+        : chrome.storage.local;
+
+const DEFAULT_STATE = {
+    hasWallet: false,
+    wallets: [],
+    trackedTokens: [],
+    rpcUrl: "https://eth.llamarpc.com",
+};
+
+const state = {
+    ...DEFAULT_STATE,
+    selectedWallet: null,
+    selectedAddress: null,
+};
+
+async function saveState() {
+    const persisted = {
+        hasWallet: state.hasWallet,
+        wallets: state.wallets,
+        trackedTokens: state.trackedTokens,
+        rpcUrl: state.rpcUrl,
+    };
+    await storageApi.set({ autistmask: persisted });
+}
+
+async function loadState() {
+    const result = await storageApi.get("autistmask");
+    if (result.autistmask) {
+        const saved = result.autistmask;
+        state.hasWallet = saved.hasWallet;
+        state.wallets = saved.wallets || [];
+        state.trackedTokens = saved.trackedTokens || [];
+        state.rpcUrl = saved.rpcUrl || DEFAULT_STATE.rpcUrl;
+    }
+}
+
+function currentAddress() {
+    if (state.selectedWallet === null || state.selectedAddress === null) {
+        return null;
+    }
+    return state.wallets[state.selectedWallet].addresses[state.selectedAddress];
+}
+
+module.exports = { state, saveState, loadState, currentAddress };