i18n(channel): explain case-insensitive matching in pricing conflict messages (#3394)

Update the modelConflict / mappingConflict strings (en + zh) to state that
model names are matched case-insensitively, so an existing entry (e.g.
"GLM-5.2") already covers all case variants and the lowercase variant does not
need to be added. This addresses the confusion in #3394 where the rejection of
a case-only duplicate looked like inconsistent behavior.

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

frontend/src/i18n/locales/en.ts

@@ -2407,8 +2407,8 @@ export default {
       deleteError: 'Failed to delete channel',
       nameRequired: 'Please enter a channel name',
       duplicateModels: 'Model "{0}" appears in multiple pricing entries',
-      modelConflict: "Model patterns '{model1}' and '{model2}' conflict: overlapping match range",
-      mappingConflict: "Mapping source patterns '{model1}' and '{model2}' conflict: overlapping match range",
+      modelConflict: "Model patterns '{model1}' and '{model2}' conflict: overlapping match range. Model names are matched case-insensitively, so an existing entry already covers all case variants — no need to add the variant separately.",
+      mappingConflict: "Mapping source patterns '{model1}' and '{model2}' conflict: overlapping match range. Source patterns are matched case-insensitively, so an existing entry already covers all case variants.",
       deleteConfirm: 'Are you sure you want to delete channel "{name}"? This cannot be undone.',
       columns: {
         name: 'Name',

frontend/src/i18n/locales/zh.ts

@@ -2484,8 +2484,8 @@ export default {
       deleteError: '删除渠道失败',
       nameRequired: '请输入渠道名称',
       duplicateModels: '模型「{0}」在多个定价条目中重复',
-      modelConflict: "模型模式 '{model1}' 和 '{model2}' 冲突：匹配范围重叠",
-      mappingConflict: "模型映射源 '{model1}' 和 '{model2}' 冲突：匹配范围重叠",
+      modelConflict: "模型模式 '{model1}' 和 '{model2}' 冲突：匹配范围重叠。模型名称按大小写不敏感匹配，已有条目已覆盖其所有大小写变体，无需重复添加。",
+      mappingConflict: "模型映射源 '{model1}' 和 '{model2}' 冲突：匹配范围重叠。源模式按大小写不敏感匹配，已有条目已覆盖其所有大小写变体。",
       deleteConfirm: '确定要删除渠道「{name}」吗？此操作不可撤销。',
       columns: {
         name: '名称',