feat: add Windows support to build system

- Add make build-windows for Windows AMD64
- Update make build-all to include Windows
- Update release script to package Windows binary as .zip
- Add Windows installation instructions to docs
- Windows binary: qfs-windows-amd64.exe (~17MB)

All platforms now supported:
- Linux AMD64 (.tar.gz)
- macOS Intel/ARM (.tar.gz)
- Windows AMD64 (.zip)

Co-Authored-By: Claude Sonnet 4.5 <noreply@anthropic.com>

RELEASE_v0.2.6.md

@@ -0,0 +1,60 @@
+## Release v0.2.6 - Build & Release Improvements
+
+Minor release focused on developer experience and release automation.
+
+### Changes
+
+**Build System**
+- 🎯 Renamed binary from `quoteforge` to `qfs` (shorter, easier to type)
+- 🏷️ Added `-version` flag to display build version
+- 📦 Added Makefile with build targets for all platforms
+- 🚀 Added automated release script for multi-platform binaries
+
+**New Commands**
+```bash
+make build-release   # Optimized build with version info
+make build-all       # Build for Linux + macOS (Intel/ARM)
+make release         # Create release packages with checksums
+./bin/qfs -version   # Show version
+```
+
+**Release Artifacts**
+- Linux AMD64
+- macOS Intel (AMD64)
+- macOS Apple Silicon (ARM64)
+- Windows AMD64
+- SHA256 checksums
+
+### Installation
+
+Download the appropriate binary for your platform:
+```bash
+# Linux
+wget https://git.mchus.pro/mchus/QuoteForge/releases/download/v0.2.6/qfs-v0.2.6-linux-amd64.tar.gz
+tar -xzf qfs-v0.2.6-linux-amd64.tar.gz
+chmod +x qfs-linux-amd64
+./qfs-linux-amd64
+
+# macOS Intel
+curl -L -O https://git.mchus.pro/mchus/QuoteForge/releases/download/v0.2.6/qfs-v0.2.6-darwin-amd64.tar.gz
+tar -xzf qfs-v0.2.6-darwin-amd64.tar.gz
+chmod +x qfs-darwin-amd64
+./qfs-darwin-amd64
+
+# macOS Apple Silicon
+curl -L -O https://git.mchus.pro/mchus/QuoteForge/releases/download/v0.2.6/qfs-v0.2.6-darwin-arm64.tar.gz
+tar -xzf qfs-v0.2.6-darwin-arm64.tar.gz
+chmod +x qfs-darwin-arm64
+./qfs-darwin-arm64
+
+# Windows
+curl -L -O https://git.mchus.pro/mchus/QuoteForge/releases/download/v0.2.6/qfs-v0.2.6-windows-amd64.zip
+unzip qfs-v0.2.6-windows-amd64.zip
+qfs-windows-amd64.exe
+```
+
+### Breaking Changes
+None - fully backward compatible with v0.2.5
+
+### Full Changelog
+https://git.mchus.pro/mchus/QuoteForge/compare/v0.2.5...v0.2.6