Implement centralized version management system

[Copilot]

Previously, the version "0.1.0" was hardcoded in multiple locations throughout the codebase, making it difficult to maintain and update for releases. This PR consolidates all version management into a single, centralized system.

Changes Made

Created centralized version package (internal/version/version.go):

• Single source of truth for all version information
• Support for build-time version injection via -ldflags
• Helper functions for accessing version, commit, and build date

Updated all modules to use centralized version:

• cmd/gabs/main.go - Main application version display
• internal/gabp/client.go - GABP client handshake version
• internal/mcp/stdio_server.go - MCP server initialization
• internal/mcp/http_server.go - HTTP health endpoint and SSE connections

Added build tooling:

• Makefile with proper version injection using git information
• Support for multi-platform builds
• Updated README.md with build instructions

Usage Examples

# Simple build (uses default version)
go build ./cmd/gabs

# Build with automatic git version info (recommended)
make build

# Build with custom version
go build -ldflags "-X github.com/pardeike/gabs/internal/version.Version=v1.0.0" ./cmd/gabs

The system automatically detects git commit information when available:

$ make build && ./gabs version
gabs 61f9f50-dirty (61f9f50c4be252776ab9d9ebe6a654814e4344b8)

This eliminates the need to manually update version strings in multiple files and provides a foundation for automated release builds.

Fixes #39.

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[Copilot]

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