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/config/settings.h

@@ -186,6 +186,10 @@ public:
     bool getLowSpecMode() const { return low_spec_mode_; }
     void setLowSpecMode(bool v) { low_spec_mode_ = v; }
 
+    // Reduce motion — disables animated transitions for accessibility
+    bool getReduceMotion() const { return reduce_motion_; }
+    void setReduceMotion(bool v) { reduce_motion_ = v; }
+
     // Market — last selected exchange + pair
     std::string getSelectedExchange() const { return selected_exchange_; }
     void setSelectedExchange(const std::string& v) { selected_exchange_ = v; }
@@ -303,6 +307,7 @@ private:
     std::set<std::string> debug_categories_;
     bool theme_effects_enabled_ = true;
     bool low_spec_mode_ = false;
+    bool reduce_motion_ = false;
     std::string selected_exchange_ = "TradeOgre";
     std::string selected_pair_ = "DRGX/BTC";