Consolidate to single Add Wallet button everywhere

Welcome and main views now show one button: "Add wallet".
Private key import is accessible as a small link at the bottom
of the Add Wallet view ("Have a private key instead?").

src/popup/index.html

@@ -42,20 +42,12 @@
                     Welcome to AutistMask
                 </h1>
                 <p class="mb-3">To get started, add a wallet.</p>
-                <div class="flex flex-col gap-2">
                 <button
                     id="btn-welcome-add"
                     class="border border-border px-2 py-1 hover:bg-fg hover:text-bg cursor-pointer"
                 >
                     Add wallet
                 </button>
-                    <button
-                        id="btn-welcome-key"
-                        class="border border-border px-2 py-1 hover:bg-fg hover:text-bg cursor-pointer"
-                    >
-                        Import private key
-                    </button>
-                </div>
             </div>
 
             <!-- ============ ADD WALLET (unified create/import) ============ -->
@@ -131,6 +123,15 @@
                     id="add-wallet-error"
                     class="mt-2 border border-border border-dashed p-1 hidden"
                 ></div>
+                <div class="mt-3 text-xs text-muted">
+                    Have a private key instead?
+                    <button
+                        id="btn-add-wallet-import-key"
+                        class="underline cursor-pointer bg-transparent border-none text-fg text-xs font-mono p-0"
+                    >
+                        Import private key
+                    </button>
+                </div>
             </div>
 
             <!-- ============ IMPORT PRIVATE KEY ============ -->
@@ -217,19 +218,13 @@
                 <div id="wallet-list"></div>
 
                 <!-- add wallet button -->
-                <div class="mt-3 border-t border-border pt-2 flex gap-2">
+                <div class="mt-3 border-t border-border pt-2">
                     <button
                         id="btn-main-add-wallet"
                         class="border border-border px-2 py-1 hover:bg-fg hover:text-bg cursor-pointer"
                     >
                         + Add wallet
                     </button>
-                    <button
-                        id="btn-main-import-key"
-                        class="border border-border px-2 py-1 hover:bg-fg hover:text-bg cursor-pointer"
-                    >
-                        + Import private key
-                    </button>
                 </div>
             </div>
 

src/popup/index.js

@@ -276,7 +276,6 @@ function init() {
 
     // -- Welcome --
     $("btn-welcome-add").addEventListener("click", showAddWalletView);
-    $("btn-welcome-key").addEventListener("click", showImportKeyView);
 
     // -- Add wallet (unified create/import) --
     $("btn-generate-phrase").addEventListener("click", () => {
@@ -324,6 +323,7 @@ function init() {
     });
 
     $("btn-add-wallet-back").addEventListener("click", backFromWalletAdd);
+    $("btn-add-wallet-import-key").addEventListener("click", showImportKeyView);
 
     // -- Import private key --
     $("btn-import-key-confirm").addEventListener("click", () => {
@@ -366,7 +366,6 @@ function init() {
     });
 
     $("btn-main-add-wallet").addEventListener("click", showAddWalletView);
-    $("btn-main-import-key").addEventListener("click", showImportKeyView);
 
     // -- Address detail --
     $("address-full").addEventListener("click", () => {