Fix bit(1) import coercion and subpath login redirect; add GitHub export script

Loader: bool() on pymysql bit(1) bytes is always true - isinstallable
and isshopfloor imported as 1 for every row; route through _truthy_bit.
The employee source DB is now optional (shopdb-only imports).

Frontend: under a subpath mount the 401 interceptor stored the browser
path (mount base included) as the login redirect and the router applied
its base again (/ops/ops). New stripBase() keeps redirects base-free.

tools/export-github.sh automates the publication flow: prune + scrub +
commit into ~/projects/shopdb-flask-pub and emit a transfer bundle.

frontend/src/views/Login.vue

@@ -52,7 +52,7 @@ import { useRouter, useRoute } from 'vue-router'
 import { useAuthStore } from '../stores/auth'
 import { setupApi } from '../api'
 import { getSiteLogo } from '../utils/siteSettings'
-import { withBase } from '../utils/basePath'
+import { withBase, stripBase } from '../utils/basePath'
 
 const router = useRouter()
 const route = useRoute()
@@ -63,7 +63,9 @@ const authStore = useAuthStore()
 function postLoginTarget() {
   const redirect = route.query.redirect
   if (typeof redirect === 'string' && redirect.startsWith('/') && !redirect.startsWith('//')) {
-    return redirect
+    // Tolerate a redirect that still carries the mount base (old bookmarks,
+    // pre-fix interceptor URLs): router paths must be base-free.
+    return stripBase(redirect)
   }
   return '/'
 }