fix(deploy): 修复envsubst无法解析${VAR:-default}语法导致CDC connector注册失败

问题：
  commit 5b1f4c82 在 full-reset Step 9 中用 envsubst 替换 connector JSON 中的
  数据库凭据，但 envsubst（GNU gettext）不支持 bash 的 ${VAR:-default} 语法，
  导致 "${POSTGRES_USER:-rwa_user}" 被原样发送给 Debezium，认证失败。

修复：
  1. deploy-mining.sh load_env(): 默认值赋值改为 export，确保 envsubst 能访问
  2. connector JSON 文件: ${VAR:-default} 改为 ${VAR}，默认值由脚本 export 提供

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

backend/services/deploy-mining.sh

@@ -254,13 +254,14 @@ load_env() {
     fi
 
     # Set defaults (match docker-compose.yml settings)
-    POSTGRES_HOST="${POSTGRES_HOST:-localhost}"
-    POSTGRES_PORT="${POSTGRES_PORT:-5432}"
-    POSTGRES_USER="${POSTGRES_USER:-rwa_user}"
-    POSTGRES_PASSWORD="${POSTGRES_PASSWORD:-rwa_secure_password}"
-    KAFKA_BROKERS="${KAFKA_BROKERS:-localhost:9092}"
-    REDIS_HOST="${REDIS_HOST:-localhost}"
-    REDIS_PORT="${REDIS_PORT:-6379}"
+    # Must use export so envsubst can access these variables
+    export POSTGRES_HOST="${POSTGRES_HOST:-localhost}"
+    export POSTGRES_PORT="${POSTGRES_PORT:-5432}"
+    export POSTGRES_USER="${POSTGRES_USER:-rwa_user}"
+    export POSTGRES_PASSWORD="${POSTGRES_PASSWORD:-rwa_secure_password}"
+    export KAFKA_BROKERS="${KAFKA_BROKERS:-localhost:9092}"
+    export REDIS_HOST="${REDIS_HOST:-localhost}"
+    export REDIS_PORT="${REDIS_PORT:-6379}"
 
     # Docker container names (match docker-compose.yml container_name)
     POSTGRES_CONTAINER="${POSTGRES_CONTAINER:-rwa-postgres}"

backend/services/scripts/debezium/identity-connector.json

@@ -6,8 +6,8 @@
 
     "database.hostname": "rwa-postgres",
     "database.port": "5432",
-    "database.user": "${POSTGRES_USER:-rwa_user}",
-    "database.password": "${POSTGRES_PASSWORD:-rwa_secure_password}",
+    "database.user": "${POSTGRES_USER}",
+    "database.password": "${POSTGRES_PASSWORD}",
     "database.dbname": "rwa_identity",
 
     "topic.prefix": "cdc.identity",

backend/services/scripts/debezium/planting-connector.json

@@ -6,8 +6,8 @@
 
     "database.hostname": "rwa-postgres",
     "database.port": "5432",
-    "database.user": "${POSTGRES_USER:-rwa_user}",
-    "database.password": "${POSTGRES_PASSWORD:-rwa_secure_password}",
+    "database.user": "${POSTGRES_USER}",
+    "database.password": "${POSTGRES_PASSWORD}",
     "database.dbname": "rwa_planting",
 
     "topic.prefix": "cdc.planting",

backend/services/scripts/debezium/referral-connector.json

@@ -6,8 +6,8 @@
 
     "database.hostname": "rwa-postgres",
     "database.port": "5432",
-    "database.user": "${POSTGRES_USER:-rwa_user}",
-    "database.password": "${POSTGRES_PASSWORD:-rwa_secure_password}",
+    "database.user": "${POSTGRES_USER}",
+    "database.password": "${POSTGRES_PASSWORD}",
     "database.dbname": "rwa_referral",
 
     "topic.prefix": "cdc.referral",

backend/services/scripts/debezium/wallet-connector.json

@@ -6,8 +6,8 @@
 
     "database.hostname": "postgres",
     "database.port": "5432",
-    "database.user": "${POSTGRES_USER:-rwa_user}",
-    "database.password": "${POSTGRES_PASSWORD:-rwa_secure_password}",
+    "database.user": "${POSTGRES_USER}",
+    "database.password": "${POSTGRES_PASSWORD}",
     "database.dbname": "rwa_wallet",
 
     "topic.prefix": "cdc.wallet",