fix(ui): extend mixed channel check to both Antigravity and Anthropic accounts

Problem:
- When creating Anthropic Console accounts to groups with Antigravity accounts,
  the mixed channel warning was not triggered
- Only Antigravity accounts triggered the confirmation dialog

Solution:
- Renamed isAntigravityAccount to needsMixedChannelCheck
- Extended check to include both 'antigravity' and 'anthropic' platforms
- Updated all 8 call sites in CreateAccountModal and EditAccountModal

Changes:
- frontend/src/components/account/CreateAccountModal.vue: 4 updates
- frontend/src/components/account/EditAccountModal.vue: 4 updates

Testing:
- Frontend compilation: passed
- Backend unit tests: passed
- OAuth flow: confirmation parameter correctly passed in Step 2
- Backend compatibility: verified with checkMixedChannelRisk logic

Impact:
- Both Antigravity and Anthropic accounts now show mixed channel warning
- OAuth accounts correctly pass confirm_mixed_channel_risk parameter
- No breaking changes to existing functionality

backend/cmd/server/VERSION

@@ -1 +1 @@
-0.1.81.9
+0.1.81.10

frontend/src/components/account/CreateAccountModal.vue

@@ -2545,7 +2545,7 @@ const splitTempUnschedKeywords = (value: string) => {
     .filter((item) => item.length > 0)
 }
 
-const isAntigravityAccount = (platform: AccountPlatform) => platform === 'antigravity'
+const needsMixedChannelCheck = (platform: AccountPlatform) => platform === 'antigravity' || platform === 'anthropic'
 
 const buildMixedChannelDetails = (resp?: CheckMixedChannelResponse) => {
   const details = resp?.details
@@ -2579,7 +2579,7 @@ const openMixedChannelDialog = (opts: {
 }
 
 const withAntigravityConfirmFlag = (payload: CreateAccountRequest): CreateAccountRequest => {
-  if (isAntigravityAccount(payload.platform) && antigravityMixedChannelConfirmed.value) {
+  if (needsMixedChannelCheck(payload.platform) && antigravityMixedChannelConfirmed.value) {
     return {
       ...payload,
       confirm_mixed_channel_risk: true
@@ -2591,7 +2591,7 @@ const withAntigravityConfirmFlag = (payload: CreateAccountRequest): CreateAccoun
 }
 
 const ensureAntigravityMixedChannelConfirmed = async (onConfirm: () => Promise<void>): Promise<boolean> => {
-  if (!isAntigravityAccount(form.platform)) {
+  if (!needsMixedChannelCheck(form.platform)) {
     return true
   }
   if (antigravityMixedChannelConfirmed.value) {
@@ -2628,7 +2628,7 @@ const submitCreateAccount = async (payload: CreateAccountRequest) => {
     emit('created')
     handleClose()
   } catch (error: any) {
-    if (error.response?.status === 409 && error.response?.data?.error === 'mixed_channel_warning' && isAntigravityAccount(form.platform)) {
+    if (error.response?.status === 409 && error.response?.data?.error === 'mixed_channel_warning' && needsMixedChannelCheck(form.platform)) {
       openMixedChannelDialog({
         message: error.response?.data?.message,
         onConfirm: async () => {

frontend/src/components/account/EditAccountModal.vue

@@ -1535,7 +1535,7 @@ function toPositiveNumber(value: unknown) {
   return Math.trunc(num)
 }
 
-const isAntigravityAccount = () => props.account?.platform === 'antigravity'
+const needsMixedChannelCheck = () => props.account?.platform === 'antigravity' || props.account?.platform === 'anthropic'
 
 const buildMixedChannelDetails = (resp?: CheckMixedChannelResponse) => {
   const details = resp?.details
@@ -1569,7 +1569,7 @@ const openMixedChannelDialog = (opts: {
 }
 
 const withAntigravityConfirmFlag = (payload: Record<string, unknown>) => {
-  if (isAntigravityAccount() && antigravityMixedChannelConfirmed.value) {
+  if (needsMixedChannelCheck() && antigravityMixedChannelConfirmed.value) {
     return {
       ...payload,
       confirm_mixed_channel_risk: true
@@ -1581,7 +1581,7 @@ const withAntigravityConfirmFlag = (payload: Record<string, unknown>) => {
 }
 
 const ensureAntigravityMixedChannelConfirmed = async (onConfirm: () => Promise<void>): Promise<boolean> => {
-  if (!isAntigravityAccount()) {
+  if (!needsMixedChannelCheck()) {
     return true
   }
   if (antigravityMixedChannelConfirmed.value) {
@@ -1632,7 +1632,7 @@ const submitUpdateAccount = async (accountID: number, updatePayload: Record<stri
     emit('updated')
     handleClose()
   } catch (error: any) {
-    if (error.response?.status === 409 && error.response?.data?.error === 'mixed_channel_warning' && isAntigravityAccount()) {
+    if (error.response?.status === 409 && error.response?.data?.error === 'mixed_channel_warning' && needsMixedChannelCheck()) {
       openMixedChannelDialog({
         message: error.response?.data?.message,
         onConfirm: async () => {