Add comprehensive platform benchmark and improve documentation layout

[Irozuku]

Summary

Replaced the placeholder "Papers & Benchmarks" page with a comprehensive benchmark section that compares DashAI against leading no-code/low-code machine learning platforms, while also improving documentation layout by increasing content width for better readability of large comparison tables.

---

Type of Change

Check all that apply like this [x]:

• Backend change
• Frontend change
• CI / Workflow change
• Build / Packaging change
• Bug fix
• Documentation

---

Changes (by file)

• docs/docs/deep-dive/benchmark.md: Added a new in-depth benchmark comparing DashAI with other no-code/low-code ML platforms across a wide range of evaluation criteria, including methodology, detailed comparisons, conclusions, and references.
• docs/docs/deep-dive/papers.md: Removed the placeholder page previously reserved for future academic references and benchmarks.
• Documentation layout configuration: Increased the maximum content width to improve readability, especially for wide benchmark tables.

---

Testing (optional)

• Verify that the new benchmark page renders correctly.
• Confirm that all tables display properly without excessive horizontal scrolling.
• Ensure the removed placeholder page is no longer referenced in the documentation navigation.