Railbase core v0.5.9

Core v0.5.9 — site-shell login fixes + interactive railbase init.

Site shell (served at /)

• App-user login now targets the correct built-in auth collection _users and offers self-serve signup, so a freshly downloaded core is usable from the / site without the admin hand-creating a user first.
• Login uses the UI-kit PasswordInput (show/hide) instead of a bare input.

CLI

• railbase init is now interactive (the npm create vite model): run it with no flags at a terminal to choose the project name + template (backend only / + Vite·Preact frontend / full-stack). <name> --template flags still work for CI / non-interactive runs.

Data-resident plugin model unchanged (same pinned plugin key) — plugins install from the marketplace as before. Binaries are unsigned (Authenticode/Azure signing still deferred).