Expand Java guide with CRUD operation examples

[devin-ai-integration]

This PR expands the Java guide with CRUD operation examples using JDBC.

• Added examples for creating tables, inserting, querying, updating, and deleting records
• Included a complete example application that demonstrates all operations
• Tested all examples with a Neon database to ensure they work correctly

Link to Devin run: https://app.devin.ai/sessions/2de47749978347308cc12babd4160f44
Requested by: Daniel

[devin-ai-integration]

🤖 Devin AI Engineer

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Name	Status	Preview	Comments	Updated (UTC)
neon-next	✅ Ready (Inspect)	Visit Preview	💬 Add feedback	Mar 14, 2025 9:11am

[devin-ai-integration]

Closing due to inactivity for more than 7 days.