game,ui: add rest state tracking and rested XP bar overlay

- Track PLAYER_REST_STATE_EXPERIENCE update field for all expansions
  (WotLK=636, Classic=718, TBC=928, Turtle=718)
- Set isResting_ flag from SMSG_SET_REST_START packet
- XP bar shows rested bonus as a lighter purple overlay extending
  beyond the current fill to (currentXp + restedXp) position
- Tooltip text changes to "%u / %u XP  (+%u rested)" when bonus exists
- "zzz" indicator shown at bar right edge while resting

include/game/game_handler.hpp

@@ -640,6 +640,8 @@ public:
     // XP tracking
     uint32_t getPlayerXp() const { return playerXp_; }
     uint32_t getPlayerNextLevelXp() const { return playerNextLevelXp_; }
+    uint32_t getPlayerRestedXp() const { return playerRestedXp_; }
+    bool isPlayerResting() const { return isResting_; }
     uint32_t getPlayerLevel() const { return serverPlayerLevel_; }
     const std::vector<uint32_t>& getPlayerExploredZoneMasks() const { return playerExploredZones_; }
     bool hasPlayerExploredZoneMasks() const { return hasPlayerExploredZones_; }
@@ -2199,6 +2201,8 @@ private:
     // ---- XP tracking ----
     uint32_t playerXp_ = 0;
     uint32_t playerNextLevelXp_ = 0;
+    uint32_t playerRestedXp_ = 0;
+    bool isResting_ = false;
     uint32_t serverPlayerLevel_ = 1;
     static uint32_t xpForLevel(uint32_t level);
 

include/game/update_field_table.hpp

@@ -41,6 +41,7 @@ enum class UF : uint16_t {
     PLAYER_BYTES_2,
     PLAYER_XP,
     PLAYER_NEXT_LEVEL_XP,
+    PLAYER_REST_STATE_EXPERIENCE,
     PLAYER_FIELD_COINAGE,
     PLAYER_QUEST_LOG_START,
     PLAYER_FIELD_INV_SLOT_HEAD,