improve Parquet querying documentation with comprehensive explanations

[drmingdrmer]

Changelog

improve Parquet querying documentation with comprehensive explanations

Enhanced the Parquet files documentation with detailed explanations of syntax, parameters, and step-by-step tutorial guidance while preserving all existing examples.

improve NDJSON querying documentation with context and explanations

• Add comprehensive introduction explaining what NDJSON is and its advantages
• Provide concrete NDJSON data examples showing realistic book catalog data
• Add detailed explanations for all existing code examples including syntax breakdown
• Explain metadata columns usage and practical use cases
• Add related documentation links for better navigation
• Enhance tutorial flow with clear step-by-step context

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Name	Status	Preview	Comments	Updated (UTC)
databend	✅ Ready (Inspect)	Visit Preview	💬 Add feedback	Aug 6, 2025 3:26am

[BohuTANG]

@drmingdrmer

This PR is high priority: #2645, but it may conflict with this one. I will merge PR 2645 first, then come back to this PR with improvements.

[drmingdrmer]

@drmingdrmer

This PR is high priority: #2645, but it may conflict with this one. I will merge PR 2645 first, then come back to this PR with improvements.

[BohuTANG]

I'll check and update the items related to this PR with consistent styling. Temporarily closing this PR.