docs: add cross-platform instructions (Linux/Windows)

[vavasilva]

Summary

Add installation and service setup instructions for Linux and Windows users.

Changes

Installation Instructions

• Ollama: Added Linux (curl installer) and Windows (download link)
• llama.cpp: Added Linux (build from source) and Windows (pre-built binaries)

Service Setup (run llama-server automatically)

• macOS: launchd (already existed)
• Linux: systemd service unit
• Windows: Task Scheduler + PowerShell script, and NSSM alternative

Format

Used collapsible <details> sections to keep the README clean while providing comprehensive instructions for each platform.

Platforms Supported

Feature	macOS	Linux	Windows
Ollama install	✅ brew	✅ curl	✅ installer
llama.cpp install	✅ brew	✅ build	✅ releases
Service setup	✅ launchd	✅ systemd	✅ Task Scheduler/NSSM

🤖 Generated with Claude Code