Optimize cookie parsing and fix missing return statement

[cdenicola]

Optimize cookie parsing and fix missing return statement

Summary

This PR implements two key efficiency improvements and includes a comprehensive analysis report:

1. Cookie Parsing Optimization: Replaced inefficient forEach loop with reduce() method in getAppCookies() function (app/helper/auth.js)
2. Missing Return Statement Fix: Added missing return statement in /auth endpoint to prevent duplicate response sending for admin users (app/index.js)
3. Efficiency Analysis Report: Added comprehensive documentation of all efficiency issues found in the codebase

These changes improve performance for every authenticated request and fix a bug where admin users would receive duplicate response messages.

Review & Testing Checklist for Human

• Test complete authentication flow: Login as both admin and regular user, verify cookies are set correctly and authentication works end-to-end
• Verify admin endpoint behavior: Access /auth as admin user and confirm only one response is sent (not duplicate messages)
• Test cookie parsing edge cases: Try various cookie formats, multiple cookies, and malformed cookies to ensure parsing robustness
• Regression testing: Verify all existing endpoints (/user, /hello, /login, /logout) still function correctly
• Performance verification: Although hard to measure directly, confirm no noticeable performance degradation in authentication-heavy workflows

Diagram

%%{ init : { "theme" : "default" }}%%
graph TD
    A["app/index.js<br/>Main Express App"]:::major-edit
    B["app/helper/auth.js<br/>Authentication Helper"]:::major-edit
    C["app/helper/secrets.js<br/>User Data"]:::context
    D["EFFICIENCY_REPORT.md<br/>Analysis Report"]:::major-edit
    
    A -->|"uses getUserId()"| B
    A -->|"imports"| C
    B -->|"parses cookies with<br/>optimized reduce()"| B
    A -->|"fixed missing return<br/>in /auth endpoint"| A
    
    subgraph Legend
        L1["Major Edit"]:::major-edit
        L2["Minor Edit"]:::minor-edit
        L3["Context/No Edit"]:::context
    end

classDef major-edit fill:#90EE90
classDef minor-edit fill:#87CEEB
classDef context fill:#FFFFFF

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Notes

• The cookie parsing optimization affects every authenticated request, so thorough testing is critical
• The original forEach approach created unnecessary function call overhead; reduce is more efficient and functional
• The missing return statement was causing both admin and non-admin responses to be sent for admin users
• All other efficiency issues documented in the report (synchronous XMLHttpRequest, unnecessary console.log, etc.) were identified but not fixed in this PR to keep scope focused

Link to Devin run: https://app.devin.ai/sessions/e2810f3a02c546fa8da1728e7b333c28
Requested by: @cdenicola