refactor: update component names to use kebab-case for consistency

src/views/errors/Forbidden.vue

@@ -1,5 +1,5 @@
 <template>
-  <ErrorShell
+  <error-shell
     :code="403"
     color="warning"
     description="你沒有權限存取此頁面或操作。"

src/views/errors/Maintenance.vue

@@ -1,5 +1,5 @@
 <template>
-  <ErrorShell
+  <error-shell
     code="MAINTENANCE"
     color="info"
     description="目前系統正在維護，請稍後再試。"

src/views/errors/NetworkError.vue

@@ -1,5 +1,5 @@
 <template>
-  <ErrorShell
+  <error-shell
     code="NETWORK"
     color="warning"
     description="無法連線到伺服器，請檢查網路或稍後再試。"

src/views/errors/NotFound.vue

@@ -1,5 +1,5 @@
 <template>
-  <ErrorShell
+  <error-shell
     :code="404"
     color="info"
     description="你輸入的網址不存在，或頁面已被移除。"

src/views/errors/ServerError.vue

@@ -1,5 +1,5 @@
 <template>
-  <ErrorShell
+  <error-shell
     :code="500"
     color="error"
     description="伺服器發生非預期錯誤，請稍後再試。"

src/views/errors/ServiceUnavailable.vue

@@ -1,5 +1,5 @@
 <template>
-  <ErrorShell
+  <error-shell
     :code="503"
     color="warning"
     description="服務目前無法使用，請稍後再試。"