Fix container logging visibility

Changes:
- Add -u flag to Python in Dockerfile to disable output buffering
- Add startup messages in main.py showing bot configuration
- Logs now appear immediately in kubectl logs output

This fixes the issue where no logs were visible when running
in Kubernetes pods due to Python's default stdout buffering.

main.py

@@ -6,6 +6,8 @@ from bot import MastodonRSSBot
 
 def main():
     """Initialize and run the bot with environment configuration"""
+    print("Starting Mastodon RSS Bot...")
+
     # Load configuration from environment variables
     bot = MastodonRSSBot(
         client_id=os.environ["MASTODON_CLIENT_ID"],
@@ -20,6 +22,16 @@ def main():
         ),
     )
 
+    print(f"Bot configured successfully:")
+    print(f"  Instance: {os.environ['MASTODON_INSTANCE_URL']}")
+    print(f"  Feed URL: {os.environ['RSS_FEED_URL']}")
+    print(f"  Visibility: {os.environ.get('TOOT_VISIBILITY', 'public')}")
+    print(f"  Check interval: {os.environ.get('CHECK_INTERVAL', '300')} seconds")
+    print(
+        f"  State file: {os.environ.get('PROCESSED_ENTRIES_FILE', '/state/processed_entries.txt')}"
+    )
+    print()
+
     # Start the bot
     bot.run()