refactor: move credentials to .env and add python-dotenv support

Replace hardcoded database credentials, ntfy tokens, and Uptime Kuma
push URLs with environment variable lookups via python-dotenv.
Add .env.example template and update .gitignore to exclude .env.

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

config/app_settings.py

@@ -19,9 +19,9 @@ LOG_TABLE_CONFIG = {
 # 从原 config.py 抽取
 NTFY_CONFIG = {
     'enabled': True,
-    'server_url': 'https://ntfy.server10086.icu',
-    'topic': 'bld',
-    'token': 'tk_eop5fs66acxtwxf6vlkiojhdvkgb0',
+    'server_url': os.environ.get('NTFY_SERVER_URL', ''),
+    'topic': os.environ.get('NTFY_TOPIC', ''),
+    'token': os.environ.get('NTFY_TOKEN', ''),
     'priority': {
         'error': 'high',
         'critical': 'urgent'
@@ -32,14 +32,14 @@ NTFY_CONFIG = {
 # 增量同步服务心跳
 UPTIME_KUMA_CONFIG = {
     'enabled': True,
-    'push_url': 'https://uptimekuma.server10086.icu/api/push/clMSgOQs4CJeF7DJAOiHaFaaZzoL8eB9',
+    'push_url': os.environ.get('UPTIME_KUMA_PUSH_URL', ''),
     'heartbeat_interval': 59  # 心跳间隔(秒)，需要与 Uptime Kuma 设置一致
 }
 
 # Excel 同步服务心跳
 EXCEL_SYNC_UPTIME_KUMA_CONFIG = {
     'enabled': True,
-    'push_url': 'https://uptimekuma.server10086.icu/api/push/MEXi5DYnC3nTMs2OfMqdelK3FawymtVY',
+    'push_url': os.environ.get('EXCEL_SYNC_UPTIME_KUMA_PUSH_URL', ''),
     'heartbeat_interval': 59  # 心跳间隔(秒)，需要与 Uptime Kuma 设置一致
 }