Add GITEA_API_TOKEN documentation to .env.example

Users need GITEA_API_TOKEN for automatic webhook setup during deployment.
Marked as optional with clear instructions on where to get it.

🤖 Generated with [Claude Code](https://claude.com/claude-code)

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

.env.example

@@ -67,6 +67,10 @@ DB_PASSWORD=
 # ===================================
 # Get your SAAC_API_KEY from: https://apps.startanaicompany.com/api/v1/register
 # Set as environment variable: export SAAC_API_KEY="your_key_here"
+#
+# GITEA_API_TOKEN is optional - only needed for automatic webhook setup
+# Get from: https://git.startanaicompany.com → Settings → Applications → Generate New Token
+# Set as environment variable: export GITEA_API_TOKEN="your_token_here"
 
 # ===================================
 # Feature Configuration