Detect framework from a file manifest

Detects the project's framework/stack from an uploaded filename listing plus the contents of key manifest files. Returns the canonical stack, a suggested protocol (static_hosting or managed_vps), the static-hosting preset (output directory and SPA mode), and suggested build commands — the same detection pipeline the web onboarding wizard uses. Files not uploaded degrade detection precision gracefully; they never error. When AI features are enabled for the account and the rule-based result is ambiguous, AI services are consulted and their results merged into the response.