feat(files,generation,specs): introduce file management, code generat…

[moabualruz]

…ion, and specification system

• Add ricecoder-files crate with comprehensive file management capabilities including atomic writes, transactions, backups, conflict detection, and audit trails
• Implement file manager with transaction support for multi-file operations and rollback functionality
• Add backup and restoration system with integrity verification and content hashing
• Implement conflict detection and resolution mechanisms for concurrent file modifications
• Add git integration for version control operations and change tracking
• Implement audit trail system for tracking all file operations with timestamps and metadata
• Add ricecoder-generation crate with template engine and boilerplate code generation
• Implement template discovery, loading, parsing, and caching mechanisms
• Add template validation and placeholder resolution with case transformation support
• Implement boilerplate generation with deterministic rendering and idempotence guarantees
• Add ricecoder-specs crate with specification management and workflow system
• Implement spec validation, inheritance, and circular dependency detection
• Add conversation history preservation and AI writer integration
• Implement steering context management and approval workflows
• Add comprehensive property-based tests for all three crates covering edge cases and invariants
• Add integration tests for multi-file transactions, git operations, and workflow phases
• Update Cargo.lock and Cargo.toml with new dependencies and workspace configuration
• Update README.md with documentation for new modules