Implement comprehensive template management and validation

[solrevdev]

Description:

Add advanced template management features including validation, versioning, inheritance, and a template marketplace concept.

Acceptance Criteria:

•  seedfolder template command group for template operations

•  Template validation with detailed error reporting

•  Template inheritance and composition support

•  Template versioning and compatibility checking

•  Template metadata management (author, version, description)

Technical Details:

• Template schema definition and validation engine

• Template inheritance system with base template support

• Version compatibility matrix for template dependencies

• Command structure: validate, list, info, install, remove

All issues build upon the completed Issue #9 foundation and can be implemented independently.

[solrevdev]

Consolidated into comprehensive Issue #15: Add External Template Sources, Configuration System, and Template Management