MultiSite: one instance serves authentication across many domains (#4)

- Serve multiple domains (RP IDs) from one instance: host-based dispatch,
  per-domain credentials and sessions, domains managed at runtime in the
  admin UI — previously one RP per instance
- Cross-domain sign-in via Related Origin Requests: per-domain related-origins
  list with a served .well-known/webauthn document
- Explicit per-domain origin lists with shell-glob wildcards (**. for apex +
  any subdomain depth, *. for one level), editable in the admin UI with
  validation and self-lockout guards
- Per-domain auth hosts: the account/admin UI can live on a different host
  per domain, no longer confined to subdomains of a single RP
- CLI: 'paskia init <rp-id [rp-name]' initializes or adds a domain to an
  existing database; 'paskia migrate' converts legacy databases

BREAKING CHANGES (v2.0):
- Database schema: config is now per-domain and credentials/sessions carry
  an rp_id — existing databases must be converted with 'paskia migrate'
- Origins are now explicit: main implicitly allowed every subdomain of the
  RP; configure '**.' origins to reproduce that behavior
- CLI: the flat '--rp-id/--rp-name/--origin/--auth/--save' flags are
  replaced by the 'init' and 'migrate' subcommandsReviewed-on: #4

scripts/fastapi-vue/buildhook.py

@@ -0,0 +1,19 @@
+# ruff: noqa: INP001
+"""Hatch build hook for building Vue frontend during package build."""
+
+import sys
+from pathlib import Path
+
+from hatchling.builders.hooks.plugin.interface import BuildHookInterface
+
+sys.path.insert(0, str(Path(__file__).parent))
+from buildutil import build
+
+
+class CustomBuildHook(BuildHookInterface):  # type: ignore[misc]
+    """Hatch build hook that builds Vue frontend during package build."""
+
+    def initialize(self, version: str, build_data: dict) -> None:  # type: ignore[override]
+        """Build frontend before package is built."""
+        super().initialize(version, build_data)
+        build("frontend")