test(channelserver): add handler tests for session, gacha, shop, and plate

Cover critical paths that previously had no test coverage:
- Session: login success/error paths, ping, logkey, record log,
  global sema lock/unlock, rights reload, announce
- Gacha: point queries, coin deduction, item receive with overflow
  and freeze, normal/stepup/box gacha play, stepup status lifecycle,
  weighted random selection
- Shop: enumeration across all shop types, exchange purchases,
  fpoint-to-item and item-to-fpoint exchange, fpoint exchange list
  with Z2 vs ZZ encoding
- Plate: load/save for platedata, platebox, platemyset with
  oversized payload rejection, diff path, and cache invalidation

Add mockSessionRepo, mockGachaRepo, mockShopRepo, and
mockUserRepoGacha to support the new test scenarios. Add
loadColumnErr field to mockCharacterRepo for diff-path error
testing.

server/channelserver/repo_mocks_test.go

@@ -110,9 +110,10 @@ type mockCharacterRepo struct {
 	strings map[string]string
 	bools   map[string]bool
 
-	adjustErr error
-	readErr   error
-	saveErr   error
+	adjustErr     error
+	readErr       error
+	saveErr       error
+	loadColumnErr error
 
 	// LoadSaveData mock fields
 	loadSaveDataID   uint32
@@ -167,7 +168,12 @@ func (m *mockCharacterRepo) SaveTime(_ uint32, column string, value time.Time) e
 	return m.saveErr
 }
 
-func (m *mockCharacterRepo) LoadColumn(_ uint32, column string) ([]byte, error)     { return m.columns[column], nil }
+func (m *mockCharacterRepo) LoadColumn(_ uint32, column string) ([]byte, error) {
+	if m.loadColumnErr != nil {
+		return nil, m.loadColumnErr
+	}
+	return m.columns[column], nil
+}
 func (m *mockCharacterRepo) SaveColumn(_ uint32, column string, data []byte) error   { m.columns[column] = data; return m.saveErr }
 func (m *mockCharacterRepo) GetName(_ uint32) (string, error)                        { return "TestChar", nil }
 func (m *mockCharacterRepo) GetUserID(_ uint32) (uint32, error)                      { return 1, nil }
@@ -735,3 +741,199 @@ func (m *mockHouseRepoForItems) GetWarehouseEquipData(_ uint32, _ uint8) ([]byte
 func (m *mockHouseRepoForItems) SetWarehouseEquipData(_ uint32, _ uint8, _ []byte) error       { return nil }
 func (m *mockHouseRepoForItems) GetTitles(_ uint32) ([]Title, error)                           { return nil, nil }
 func (m *mockHouseRepoForItems) AcquireTitle(_ uint16, _ uint32) error                         { return nil }
+
+// --- mockSessionRepo ---
+
+type mockSessionRepo struct {
+	validateErr error
+	bindErr     error
+	clearErr    error
+	updateErr   error
+
+	boundToken  string
+	clearedToken string
+}
+
+func (m *mockSessionRepo) ValidateLoginToken(_ string, _ uint32, _ uint32) error { return m.validateErr }
+func (m *mockSessionRepo) BindSession(token string, _ uint16, _ uint32) error {
+	m.boundToken = token
+	return m.bindErr
+}
+func (m *mockSessionRepo) ClearSession(token string) error {
+	m.clearedToken = token
+	return m.clearErr
+}
+func (m *mockSessionRepo) UpdatePlayerCount(_ uint16, _ int) error { return m.updateErr }
+
+// --- mockGachaRepo ---
+
+type mockGachaRepo struct {
+	// GetEntryForTransaction
+	txItemType   uint8
+	txItemNumber uint16
+	txRolls      int
+	txErr        error
+
+	// GetRewardPool
+	rewardPool    []GachaEntry
+	rewardPoolErr error
+
+	// GetItemsForEntry
+	entryItems    map[uint32][]GachaItem
+	entryItemsErr error
+
+	// GetGuaranteedItems
+	guaranteedItems []GachaItem
+
+	// Stepup
+	stepupStep    uint8
+	stepupTime    time.Time
+	stepupErr     error
+	hasEntryType  bool
+	deletedStepup bool
+	insertedStep  uint8
+
+	// Box
+	boxEntryIDs    []uint32
+	boxEntryIDsErr error
+	insertedBoxIDs []uint32
+	deletedBox     bool
+
+	// Shop
+	gachas       []Gacha
+	listShopErr  error
+	shopType     int
+	allEntries   []GachaEntry
+	allEntriesErr error
+	weightDivisor float64
+
+	// FrontierPoints from gacha
+	addFPErr error
+}
+
+func (m *mockGachaRepo) GetEntryForTransaction(_ uint32, _ uint8) (uint8, uint16, int, error) {
+	return m.txItemType, m.txItemNumber, m.txRolls, m.txErr
+}
+func (m *mockGachaRepo) GetRewardPool(_ uint32) ([]GachaEntry, error) {
+	return m.rewardPool, m.rewardPoolErr
+}
+func (m *mockGachaRepo) GetItemsForEntry(entryID uint32) ([]GachaItem, error) {
+	if m.entryItemsErr != nil {
+		return nil, m.entryItemsErr
+	}
+	if m.entryItems != nil {
+		return m.entryItems[entryID], nil
+	}
+	return nil, nil
+}
+func (m *mockGachaRepo) GetGuaranteedItems(_ uint8, _ uint32) ([]GachaItem, error) {
+	return m.guaranteedItems, nil
+}
+func (m *mockGachaRepo) GetStepupStep(_ uint32, _ uint32) (uint8, error) {
+	return m.stepupStep, m.stepupErr
+}
+func (m *mockGachaRepo) GetStepupWithTime(_ uint32, _ uint32) (uint8, time.Time, error) {
+	return m.stepupStep, m.stepupTime, m.stepupErr
+}
+func (m *mockGachaRepo) HasEntryType(_ uint32, _ uint8) (bool, error) {
+	return m.hasEntryType, nil
+}
+func (m *mockGachaRepo) DeleteStepup(_ uint32, _ uint32) error {
+	m.deletedStepup = true
+	return nil
+}
+func (m *mockGachaRepo) InsertStepup(_ uint32, step uint8, _ uint32) error {
+	m.insertedStep = step
+	return nil
+}
+func (m *mockGachaRepo) GetBoxEntryIDs(_ uint32, _ uint32) ([]uint32, error) {
+	return m.boxEntryIDs, m.boxEntryIDsErr
+}
+func (m *mockGachaRepo) InsertBoxEntry(_ uint32, entryID uint32, _ uint32) error {
+	m.insertedBoxIDs = append(m.insertedBoxIDs, entryID)
+	return nil
+}
+func (m *mockGachaRepo) DeleteBoxEntries(_ uint32, _ uint32) error {
+	m.deletedBox = true
+	return nil
+}
+func (m *mockGachaRepo) ListShop() ([]Gacha, error)               { return m.gachas, m.listShopErr }
+func (m *mockGachaRepo) GetShopType(_ uint32) (int, error)         { return m.shopType, nil }
+func (m *mockGachaRepo) GetAllEntries(_ uint32) ([]GachaEntry, error) {
+	return m.allEntries, m.allEntriesErr
+}
+func (m *mockGachaRepo) GetWeightDivisor(_ uint32) (float64, error) { return m.weightDivisor, nil }
+
+// --- mockShopRepo ---
+
+type mockShopRepo struct {
+	shopItems       []ShopItem
+	shopItemsErr    error
+	purchases       []shopPurchaseRecord
+	recordErr       error
+	fpointQuantity  int
+	fpointValue     int
+	fpointItemErr   error
+	fpointExchanges []FPointExchange
+}
+
+type shopPurchaseRecord struct {
+	charID, itemHash, quantity uint32
+}
+
+func (m *mockShopRepo) GetShopItems(_ uint8, _ uint32, _ uint32) ([]ShopItem, error) {
+	return m.shopItems, m.shopItemsErr
+}
+func (m *mockShopRepo) RecordPurchase(charID, itemHash, quantity uint32) error {
+	m.purchases = append(m.purchases, shopPurchaseRecord{charID, itemHash, quantity})
+	return m.recordErr
+}
+func (m *mockShopRepo) GetFpointItem(_ uint32) (int, int, error) {
+	return m.fpointQuantity, m.fpointValue, m.fpointItemErr
+}
+func (m *mockShopRepo) GetFpointExchangeList() ([]FPointExchange, error) {
+	return m.fpointExchanges, nil
+}
+
+// --- mockUserRepoGacha (UserRepo with configurable gacha fields) ---
+
+type mockUserRepoGacha struct {
+	mockUserRepoForItems
+
+	gachaFP, gachaGP, gachaGT uint32
+	trialCoins                 uint16
+	deductTrialErr             error
+	deductPremiumErr           error
+	deductFPErr                error
+	addFPFromGachaErr          error
+
+	fpDeductBalance uint32
+	fpDeductErr     error
+	fpCreditBalance uint32
+	fpCreditErr     error
+
+	setLastCharErr error
+	rights         uint32
+	rightsErr      error
+}
+
+func (m *mockUserRepoGacha) GetGachaPoints(_ uint32) (uint32, uint32, uint32, error) {
+	return m.gachaFP, m.gachaGP, m.gachaGT, nil
+}
+func (m *mockUserRepoGacha) GetTrialCoins(_ uint32) (uint16, error)    { return m.trialCoins, nil }
+func (m *mockUserRepoGacha) DeductTrialCoins(_ uint32, _ uint32) error { return m.deductTrialErr }
+func (m *mockUserRepoGacha) DeductPremiumCoins(_ uint32, _ uint32) error {
+	return m.deductPremiumErr
+}
+func (m *mockUserRepoGacha) DeductFrontierPoints(_ uint32, _ uint32) error { return m.deductFPErr }
+func (m *mockUserRepoGacha) AddFrontierPointsFromGacha(_ uint32, _ uint32, _ uint8) error {
+	return m.addFPFromGachaErr
+}
+func (m *mockUserRepoGacha) AdjustFrontierPointsDeduct(_ uint32, _ int) (uint32, error) {
+	return m.fpDeductBalance, m.fpDeductErr
+}
+func (m *mockUserRepoGacha) AdjustFrontierPointsCredit(_ uint32, _ int) (uint32, error) {
+	return m.fpCreditBalance, m.fpCreditErr
+}
+func (m *mockUserRepoGacha) SetLastCharacter(_ uint32, _ uint32) error { return m.setLastCharErr }
+func (m *mockUserRepoGacha) GetRights(_ uint32) (uint32, error)       { return m.rights, m.rightsErr }