Implement complete talent system with dual spec support

Network Protocol:
- Add SMSG_TALENTS_INFO (0x4C0) packet parsing for talent data
- Add CMSG_LEARN_TALENT (0x251) to request learning talents
- Add MSG_TALENT_WIPE_CONFIRM (0x2AB) opcode for spec switching
- Parse talent spec, unspent points, and learned talent ranks

DBC Parsing:
- Load Talent.dbc: talent grid positions, ranks, prerequisites, spell IDs
- Load TalentTab.dbc: talent tree definitions with correct field indices
- Fix localized string field handling (17 fields per string)
- Load Spell.dbc and SpellIcon.dbc for talent icons and tooltips
- Class mask filtering using bitwise operations (1 << (class - 1))

UI Implementation:
- Complete talent tree UI with tabbed interface for specs
- Display talent icons from spell data with proper tinting/borders
- Enhanced tooltips: spell name, rank, current/next descriptions, prereqs
- Visual states: green (maxed), yellow (partial), white (available), gray (locked)
- Tier unlock system (5 points per tier requirement)
- Rank overlay on icons with shadow text
- Click to learn talents with validation

Dual Spec Support:
- Store unspent points and learned talents per spec (0 and 1)
- Track active spec and display its talents
- Spec switching UI with buttons for Spec 1/Spec 2
- Handle both SMSG_TALENTS_INFO packets from server at login
- Display unspent points for both specs in header
- Independent talent trees for each specialization

include/ui/game_screen.hpp

@@ -145,6 +145,7 @@ private:
 
     // ---- New UI renders ----
     void renderActionBar(game::GameHandler& gameHandler);
+    void renderBagBar(game::GameHandler& gameHandler);
     void renderXpBar(game::GameHandler& gameHandler);
     void renderCastBar(game::GameHandler& gameHandler);
     void renderCombatText(game::GameHandler& gameHandler);
@@ -195,6 +196,10 @@ private:
     int actionBarDragSlot_ = -1;
     GLuint actionBarDragIcon_ = 0;
 
+    // Bag bar textures
+    GLuint backpackIconTexture_ = 0;
+    GLuint emptyBagSlotTexture_ = 0;
+
     static std::string getSettingsPath();
 
     // Gender placeholder replacement