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/utils/basePath.js

@@ -11,3 +11,15 @@ export function withBase(path) {
   if (/^([a-z]+:)?\/\//i.test(path) || path.startsWith('data:')) return path
   return BASE_URL + String(path).replace(/^\//, '')
 }
+
+// Inverse of withBase: turn a browser pathname (which includes the mount
+// base, e.g. '/ops/computers') into a router path ('/computers'). Router
+// navigation already applies the base; feeding it an un-stripped pathname
+// double-prefixes ('/ops/ops/...').
+export function stripBase(path) {
+  if (!path) return path
+  if (BASE_URL !== '/' && path.startsWith(BASE_URL)) {
+    return '/' + path.slice(BASE_URL.length)
+  }
+  return path
+}