docs: improve developer onboarding in README

[fttawa]

Summary

• Adds an English Development Setup section to README.md with the local static-server flow using npx serve ..
• Replaces the outdated repository structure block with a current Project Structure overview that matches the actual repository layout.
• Keeps the change scoped to README.md only and links to the existing Swagger UI, Dev Portal, and Chain Explorer instead of duplicating the Dev Portal content.

Codebase verification answer

• marketplace-social.html loads the root-level marketplace-social.js via <script src="marketplace-social.js?...">.
• A second copy exists at js/marketplace-social.js, but the marketplace page uses the file at the HTML root.
• The main local API proxy file is api-proxy.js; api-proxy-enhanced.js contains the larger enhanced simulation layer.

Validation

• git diff --check
• Confirmed README references with rg for Development Setup, npx serve ., Project Structure, marketplace-social.js, api-proxy.js, Swagger UI, Dev Portal, and Chain Explorer.
• Verified live links returned HTTP 200:
  • https://latanda.online/docs
  • https://latanda.online/dev-dashboard.html
  • https://exp.utsa.tech/latanda/staking

Closes #50

[github-actions]

PR Gatekeeper

• Bounty issue 📖 Developer Documentation Page — 50 LTD Bounty #50 is not assigned to you. Comment on the issue with your proposal and wait for assignment. See CONTRIBUTING.md.

This PR has been automatically closed. Follow the process in CONTRIBUTING.md and try again.

[github-actions]

Welcome @fttawa!

Thanks for your first PR to La Tanda.

Before review, please confirm:

• I read the Codebase Patterns section in CONTRIBUTING.md
• Auth token uses localStorage.getItem('auth_token') (not sessionStorage or other keys)
• All user data in HTML uses escapeHtml()
• UI text is in Spanish, code comments in English
• API endpoints verified against Swagger UI
• I modified existing files (not created standalone scripts)

Resources

• CONTRIBUTING.md — Codebase patterns and rules
• Swagger UI — API documentation (220+ endpoints)
• Dev Portal — Interactive sandbox and SDK examples

A maintainer will review your PR within 24-48 hours.

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Automated message for first-time contributors

[fttawa]

Acknowledged the gatekeeper result: #50 is not assigned to me yet, so I am leaving this PR closed for now instead of repeatedly reopening it.

I posted a standard /claim #50 follow-up on the issue with the verification answer and will reopen/resubmit this same README-only patch once the issue is assigned.

[fttawa]

Checklist response to the bot prompt:

• CONTRIBUTING.md#Codebase Patterns appears to be unavailable on main right now (CONTRIBUTING.md is not present in the repository tree), so I could not read that missing section directly.
• Auth token handling is not touched by this PR; the change is README-only.
• User data rendering / escapeHtml() is not touched by this PR; the change is README-only.
• UI text/code comment convention is not affected. This bounty explicitly asks for developer-facing README text in English.
• API/docs links were verified: Swagger UI, Dev Portal, and Chain Explorer returned HTTP 200 during validation.
• Existing files only: this PR modifies README.md only and creates no new docs files.

The current blocker remains the gatekeeper requirement that issue #50 must be assigned to me before review. I will reopen/resubmit after assignment.