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/api/index.js

@@ -1,5 +1,5 @@
 import axios from 'axios'
-import { withBase } from './../utils/basePath'
+import { withBase, stripBase } from './../utils/basePath'
 
 // BASE_URL ends in '/', so this is '/api' at root or '/ops/api' under a subpath
 // mount. Keeps the SPA, its API, and IIS all on the same mount path.
@@ -35,8 +35,10 @@ api.interceptors.response.use(
       // Preserve the destination so login returns the user to this page.
       if (hadToken) {
         const loginPath = withBase('/login')
-        const here = window.location.pathname + window.location.search
-        const target = here && here !== loginPath
+        // Router paths exclude the mount base; strip it or login's
+        // router.push double-prefixes under a subpath mount.
+        const here = stripBase(window.location.pathname) + window.location.search
+        const target = here && here !== '/login'
           ? loginPath + '?redirect=' + encodeURIComponent(here)
           : loginPath
         window.location.href = target