Add the printedparts plugin: 3D-printed parts storefront and kiosk

Catalog with photos and append-only print-file revisions, a stock
ledger attributing every take/restock/adjust to a badge-resolved
employee, a touch kiosk (scan bin, scan badge, keypad quantity) with a
deliberately open decrement-only take endpoint, 1x0.5in CODE128 bin
labels, low-stock email alerts to selected users, roles, or addresses,
and stock/consumption/by-person reports with a cache-vs-ledger
reconcile. Ships disabled; enable per site. Contract 0.13.0 adds the
mailer and the User/Role models to the plugin surface.

plugins/printedparts/services/badges.py

@@ -0,0 +1,69 @@
+"""Badge resolution for the printedparts plugin.
+
+Same input contract as the USB plugin (deliberately copied, not imported -
+cross-plugin imports break the shopdb.api-only contract):
+
+- all digits            -> an SSO typed or scanned directly
+- 0<digits>BZ           -> a physical badge wrapping a PayNo (keyboard-wedge
+                           scanners emit this shape)
+- anything else         -> unresolvable
+
+Names come from the employees plugin's self-hosted directory, looked up by
+SSO. The directory carries no PayNo column, so PayNo badges resolve only when
+the wrapped digits are themselves the SSO (true at sites whose badges encode
+the SSO); otherwise they fall to the unknown-badge policy.
+
+Policy (Setting printedparts_unknown_badge): 'deny' (default) rejects a badge
+with no directory match; 'allow' records the SSO with an empty name.
+"""
+
+import re
+
+from shopdb.api import Setting
+
+_PAYNO_BADGE = re.compile(r'^0(\d+)BZ$', re.IGNORECASE)
+
+
+class BadgeError(ValueError):
+    """Raised when a badge cannot be accepted under the site policy."""
+
+
+def _directory_name(sso):
+    """Best-effort display name from the employees plugin directory."""
+    try:
+        from plugins.employees.models import DirectoryEmployee
+        from shopdb.api import db
+        if sso and str(sso).isdigit():
+            employee = db.session.get(DirectoryEmployee, int(sso))
+            if employee:
+                return f'{employee.firstname} {employee.lastname}'.strip()
+    except Exception:
+        pass
+    return None
+
+
+def resolve_badge(badge):
+    """Return (sso, name) for a scanned badge, enforcing the site policy.
+
+    Raises BadgeError with a kiosk-displayable message when the badge shape is
+    unrecognized or the policy denies an unmatched badge.
+    """
+    badge = (badge or '').strip()
+    if not badge:
+        raise BadgeError('Scan or enter a badge')
+
+    if badge.isdigit():
+        sso = badge
+    else:
+        match = _PAYNO_BADGE.match(badge)
+        if not match:
+            raise BadgeError('Unrecognized badge format')
+        sso = match.group(1)
+
+    name = _directory_name(sso)
+    if name is None:
+        policy = (Setting.get('printedparts_unknown_badge') or 'deny').lower()
+        if policy != 'allow':
+            raise BadgeError('Badge not recognized - see the parts team')
+        return sso, ''
+    return sso, name