docs: refresh project guidance and environment setup

Add env example defaults for Vite API and login settings, document
template structure and page creation flow, and align agent guidance with
current LLM development rules. Also allow committing the env example while
keeping local env files ignored.docs: refresh project guidance and environment setup

Add env example defaults for Vite API and login settings, document
template structure and page creation flow, and align agent guidance with
current LLM development rules. Also allow committing the env example while
keeping local env files ignored.

.env.example

@@ -0,0 +1,11 @@
+# Vite API base URL。
+# 使用 Vite dev proxy 時，建議維持相對路徑。
+VITE_API_BASE_URL=/service/api
+
+# 登入示範開關。只有專案明確支援略過登入時才設為 true。
+VITE_SKIP_LOGIN=false
+
+# 本機開發示範帳號。
+# 有後端或 demo 帳號時，複製到 .env.development.local 後填入。
+VITE_DEV_DEFAULT_USER_ID=
+VITE_DEV_DEFAULT_PASSWORD=