Add web professional reading gateway surface

.env.cn.example

@@ -0,0 +1,21 @@
+# Mainland China VedAstro Gateway mode.
+# Copy to .env.local on the backend host. Do not expose secrets in the browser.
+
+VEDASTRO_GATEWAY_MODE=cn_gateway
+VEDASTRO_SELF_HOST_ENDPOINT=https://your-domain.example.com/vedastro
+
+# Optional official upstream. Keep it backend-only.
+# VEDASTRO_API_ENDPOINT=https://api.vedastro.org/api
+# VEDASTRO_API_KEY=
+# VEDASTRO_ENABLE_NETWORK=0
+
+# Cache / TTL / free-tier queue. These keep ordinary users from calling upstream directly.
+VEDASTRO_CACHE_TTL_SECONDS=604800
+VEDASTRO_OFFICIAL_FULL_SNAPSHOT_CACHE_TTL_SECONDS=604800
+VEDASTRO_GATEWAY_QUEUE_ENABLED=1
+VEDASTRO_FREE_TIER_QUEUE=1
+VEDASTRO_FAIL_OPEN_LOCAL=1
+
+# Runtime guardrails.
+VEDASTRO_TIMEOUT_SECONDS=20
+VEDASTRO_FULL_CATALOG_SAMPLE_LIMIT=0