v0.12.0 — rename ollama models to local-cpu/local-cuda prefix

Breaking change: all Ollama model aliases renamed from ollama-cpu-* and
ollama-cuda-* to local-cpu-* and local-cuda-* respectively. Any client
using the old names must update.

- 19 models renamed across provider configs, fallback chains, resource
  manager, tests, and all documentation
- README intro rewritten to reflect full platform scope
- Makefile restart now uses background mode (run-bg)