🔒 fix(express): reduce json payload limit to prevent dos

[google-labs-jules]

🎯 What: Reduced the express.json limit from 50mb to 5mb.
⚠️ Risk: An excessively large JSON payload limit (50MB) allows an attacker to send very large JSON objects, leading to excessive memory allocation and potentially causing a Denial of Service (DoS) by crashing the Node.js server.
🛡️ Solution: Reduced the limit to a more reasonable size (5MB), which is still plenty for the expected payloads (text, HTML drafts, and configuration data) without exposing the application to easy resource exhaustion.

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PR created automatically by Jules for task 3803870144570734169 started by @instituto-ops

[google-labs-jules]

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