Release (v0.3.0): refactored schema structures used by the applciation

[RepoRover]

This pull request introduces significant improvements to the schema generation and documentation process for database schemas. The main changes are the introduction of multiple output schema types per database variant (including AI-focused and CLI-focused schemas), a shift to fully-resolved, self-contained engine config schemas, and updates to the documentation and code to reflect these enhancements.

Schema output and code generation improvements:

• The schema generator now produces three output files per database engine/version: tables.json (for AI agents), snapshot/stored.json, and snapshot/working.json (both for CLI use), instead of a single spec.json. The generator logic and file naming configuration have been updated accordingly. [1] [2] [3] [4]
• The output manager now provides methods to write and resolve these new schema types, and to generate URLs and output paths for each schema type per engine/version. The engine map structure in the schema map (smap.json) is updated to reflect the new schema outputs. [1] [2] [3]

Engine config schema improvements:

• Engine config schemas are now generated as fully-resolved, self-contained files (e.g., config/postgresql.json), with all $ref references inlined. The output manager includes a new method to resolve and write these files, and the schema map now references these directly. [1] [2]

Documentation updates:

• The README.md files have been updated to document the new project structure, the new output schema files and locations, and the updated schema map format. Explanations have been added for the user project structure, per-schema API keys, and the new engine config schema approach. [1] [2] [3] [4]

Codebase organization:

• The OutputManager now imports the JSONRefResolver directly, reflecting its use in resolving schemas for output.

These changes make the schema generation process more modular, clear, and suitable for both AI and CLI consumers, while simplifying integration for users and downstream tools.