Fix trainer system and add critical spell/quest opcodes

Trainer System Fixes:
- Fix CMSG_TRAINER_BUY_SPELL packet: remove incorrect trainerType field (12 bytes not 16)
- Correct spell state interpretation: 0=available, 1=unavailable, 2=known
- Add dynamic prerequisite re-evaluation in real-time as spells are learned
- Immediately update knownSpells on SMSG_TRAINER_BUY_SUCCEEDED
- Add "Show unavailable spells" checkbox filter to trainer window
- Override server state when prerequisites become met client-side

New Spell Opcodes:
- SMSG_SUPERCEDED_SPELL (0x12C): handle spell rank upgrades
- SMSG_SEND_UNLEARN_SPELLS (0x41F): handle bulk unlearning (respec/dual-spec)
- CMSG_TRAINER_LIST (0x1B0): trainer request opcode

Quest System:
- SMSG_QUESTUPDATE_COMPLETE (0x195): mark quests complete when objectives done
- Show "Quest Complete" message and enable turn-in UI

Detailed logging:
- SMSG_INITIAL_SPELLS now logs packet size and first 10 spell IDs
- Money values logged during trainer purchases
- Trainer spell states and prerequisites logged for debugging

This enables proper spell progression chains, spec changes, and quest completion
notifications matching retail WoW 3.3.5a behavior.

include/game/game_handler.hpp

@@ -495,6 +495,8 @@ public:
         std::string title;
         std::string objectives;
         bool complete = false;
+        // Objective kill counts: objectiveIndex -> (current, required)
+        std::unordered_map<uint32_t, std::pair<uint32_t, uint32_t>> killCounts;
     };
     const std::vector<QuestLogEntry>& getQuestLog() const { return questLog_; }
     void abandonQuest(uint32_t questId);
@@ -697,7 +699,9 @@ private:
     void handleCooldownEvent(network::Packet& packet);
     void handleAuraUpdate(network::Packet& packet, bool isAll);
     void handleLearnedSpell(network::Packet& packet);
+    void handleSupercededSpell(network::Packet& packet);
     void handleRemovedSpell(network::Packet& packet);
+    void handleUnlearnSpells(network::Packet& packet);
 
     // ---- Phase 4 handlers ----
     void handleGroupInvite(network::Packet& packet);

include/game/opcodes.hpp

@@ -159,7 +159,9 @@ enum class Opcode : uint16_t {
     SMSG_UPDATE_AURA_DURATION        = 0x137,
     SMSG_INITIAL_SPELLS              = 0x12A,
     SMSG_LEARNED_SPELL               = 0x12B,
+    SMSG_SUPERCEDED_SPELL            = 0x12C,
     SMSG_REMOVED_SPELL               = 0x203,
+    SMSG_SEND_UNLEARN_SPELLS         = 0x41F,
     SMSG_SPELL_DELAYED               = 0x1E2,
     SMSG_AURA_UPDATE                 = 0x3FA,
     SMSG_AURA_UPDATE_ALL             = 0x495,
@@ -223,8 +225,11 @@ enum class Opcode : uint16_t {
     SMSG_QUESTGIVER_QUEST_INVALID    = 0x18F,
     SMSG_QUESTGIVER_QUEST_COMPLETE   = 0x191,
     CMSG_QUESTLOG_REMOVE_QUEST       = 0x194,
+    SMSG_QUESTUPDATE_ADD_KILL        = 0x196,  // Quest kill count update
+    SMSG_QUESTUPDATE_COMPLETE        = 0x195,  // Quest objectives completed
     CMSG_QUEST_QUERY                 = 0x05C,  // Client requests quest data
     SMSG_QUEST_QUERY_RESPONSE        = 0x05D,  // Server sends quest data
+    SMSG_QUESTLOG_FULL               = 0x1A3,  // Full quest log on login
 
     // ---- Phase 5: Vendor ----
     CMSG_LIST_INVENTORY              = 0x19E,
@@ -235,8 +240,10 @@ enum class Opcode : uint16_t {
     SMSG_BUY_FAILED                  = 0x1A5,
 
     // ---- Trainer ----
+    CMSG_TRAINER_LIST                = 0x01B0,
     SMSG_TRAINER_LIST                = 0x01B1,
     CMSG_TRAINER_BUY_SPELL           = 0x01B2,
+    SMSG_TRAINER_BUY_FAILED          = 0x01B4,
 
     // ---- Phase 5: Item/Equip ----
     CMSG_ITEM_QUERY_SINGLE           = 0x056,

include/game/world_packets.hpp

@@ -1750,7 +1750,7 @@ public:
 
 class TrainerBuySpellPacket {
 public:
-    static network::Packet build(uint64_t trainerGuid, uint32_t trainerId, uint32_t spellId);
+    static network::Packet build(uint64_t trainerGuid, uint32_t spellId);
 };
 
 // ============================================================