feat: add generate_schema_docs tool for database documentation

[hasithasandunlakshan]

What kind of change does this PR introduce?

Feature

What is the current behavior?

Currently, to understand the full structure of a database (tables, columns, RLS policies, triggers, and functions), an AI agent or developer must call multiple tools (e.g., list_tables with verbose: true, execute_sql, etc.) or perform multiple manual queries. There is no single, consolidated way to get a documentation-ready overview of the database schema.

Relevant Issue: #277

What is the new behavior?

This PR introduces a new tool, generate_schema_docs, which provides a comprehensive, documentation-ready summary of the database schema in a single call.

Key Features:

• Consolidated View: Fetches tables, columns, foreign keys, RLS policies, triggers, and user-defined functions in one operation.
• Dual Output Formats: Supports markdown (optimized for humans/AI context windows), json (optimized for programmatic use), or both.
• Smart Filtering: Includes options to filter by specific schemas and toggle the inclusion of internal/system functions.
• RLS Awareness: Highlights whether RLS is enabled and lists policies directly under their respective tables in the markdown output.
• Architectural Alignment: Correctly integrated into the database feature group and wired into the MCP server runtime.

Additional context

• Test Coverage: Added comprehensive unit tests in server.test.ts covering various output formats and edge cases. All 172 unit tests are passing.
• Zod Integration: Fully typed input and output schemas, allowing for type-safe usage via the AI SDK.
• Performance: Uses parameterized SQL queries and grouping logic to minimize token bloat while maintaining high information density.