feat(lite): startup unlock prompt + real-backend encryption verification

Startup lock screen (soft): once the first refresh reveals the auto-opened wallet
is encrypted+locked, show the unlock modal on launch (reusing renderLiteUnlockPrompt,
one-shot per session). Soft by design — balances stay viewable via viewing keys
while locked, so the user may dismiss and browse read-only; only spending needs
the passphrase.

Real-backend verification: add `lite_smoke --encrypt` (create -> encryptionstatus
-> encrypt -> lock -> unlock, checking flags; passphrase never printed). Running it
against the real SDXL backend showed encrypt LOCKS immediately
(after encrypt: encrypted=1, locked=1) — the backend removes spending keys right
after encrypting. The controller already relays encryptionstatus faithfully (UI is
state-driven, so unaffected), but the fake modeled encrypt->unlocked; corrected the
fake (encrypt -> encrypted+locked) and the test sequence (encrypt -> unlock -> lock
-> decrypt) to match real behavior.

Builds clean, tests pass, hygiene clean.

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

tests/fake_lite_backend.h

@@ -128,10 +128,11 @@ inline char* liteFakeExecute(const char* command, const char* args)
             ++g_liteFakeSaveCount;
             return liteFakeDup("{\"result\":\"success\"}");
         }
-        // Encryption state machine. encrypt -> encrypted (keys stay in memory this session);
-        // lock/unlock toggle locked; decrypt clears it; encryptionstatus reports {encrypted,locked}.
+        // Encryption state machine. encrypt -> encrypted AND locked (matches the real backend,
+        // which removes keys from memory right after encrypting — verified via lite_smoke --encrypt);
+        // unlock/lock toggle locked; decrypt clears it; encryptionstatus reports {encrypted,locked}.
         if (std::strcmp(c, "encrypt") == 0) {
-            g_liteFakeEncrypted = true; g_liteFakeLocked = false;
+            g_liteFakeEncrypted = true; g_liteFakeLocked = true;
             return liteFakeDup("{\"result\":\"success\"}");
         }
         if (std::strcmp(c, "unlock") == 0) {