v1.2.0: UX audit — security fixes, accessibility, and polish

Security (P0):
- Fix sidebar remaining interactive behind lock screen
- Extend auto-lock idle detection to include active widget interactions
- Distinguish missing PIN vault from wrong PIN; auto-switch to passphrase

Blocking UX (P1):
- Add 15s timeout for encryption state check to prevent indefinite loading
- Show restart reason in loading overlay after wallet encryption
- Add Force Quit button on shutdown screen after 10s
- Warn user if embedded daemon fails to start during wizard completion

Polish (P2):
- Use configured explorer URL in Receive tab instead of hardcoded URL
- Increase request memo buffer from 256 to 512 bytes to match Send tab
- Extend notification duration to 5s for critical operations (tx sent,
  wallet encrypted, key import, backup, export)
- Add Reduce Motion accessibility setting (disables page fade + balance lerp)
- Show estimated remaining time during mining thread benchmark
- Add staleness indicator to market price data (warning after 5 min)

New i18n keys: incorrect_pin, incorrect_passphrase, pin_not_set,
restarting_after_encryption, force_quit, reduce_motion, tt_reduce_motion,
ago, wizard_daemon_start_failed

src/util/i18n.cpp

@@ -256,6 +256,15 @@ void I18n::loadBuiltinEnglish()
         strings_["settings_quick_unlock_pin"] = "Quick-unlock PIN";
         strings_["settings_pin_active"] = "PIN";
         strings_["settings_encrypt_first_pin"] = "Encrypt wallet first to enable PIN";
+        strings_["incorrect_pin"] = "Incorrect PIN";
+        strings_["incorrect_passphrase"] = "Incorrect passphrase";
+        strings_["pin_not_set"] = "PIN not set. Use passphrase to unlock.";
+        strings_["restarting_after_encryption"] = "Restarting daemon after encryption...";
+        strings_["force_quit"] = "Force Quit";
+        strings_["reduce_motion"] = "Reduce Motion";
+        strings_["tt_reduce_motion"] = "Disable animated transitions and balance lerp for accessibility";
+        strings_["ago"] = "ago";
+        strings_["wizard_daemon_start_failed"] = "Failed to start daemon \xe2\x80\x94 it will be retried automatically";
         strings_["settings_data_dir"] = "Data Dir:";
         strings_["settings_wallet_size_label"] = "Wallet Size:";
         strings_["settings_debug_changed"] = "Debug categories changed \xe2\x80\x94 restart daemon to apply";