printedparts stage 15: print-file revision history + role-based alerts

printeditemfiles lands as the plugin's first incremental migration
(0002 on the plugin chain - the ADR-008 payoff). Revisions are
append-only per item: upload assigns the next number, records the
uploader from the JWT, enforces an extension allowlist and a 100 MB
cap; download serves the original filename; a permission-gated delete
covers wrong-file mistakes. The detail page gains the revision table
with a current badge. Unique storedfilename is sized 191 so the index
fits MySQL's 767-byte prefix - the per-plugin chain does not apply the
core env's ROW_FORMAT hook.

Alert recipients gain roles: Role joins the 0.13.0 surface, a role
picker on the settings page, and every active member of the selected
roles is folded into the deduped recipient list.

plugins/printedparts/plugin.py

@@ -16,7 +16,7 @@ from flask import Flask, Blueprint
 from shopdb.plugins.base import BasePlugin, PluginMeta
 from shopdb.api import db, Setting
 
-from .models import PrintedItem, PrintedItemTransaction
+from .models import PrintedItem, PrintedItemTransaction, PrintedItemFile
 from .api import printedparts_bp
 
 logger = logging.getLogger(__name__)
@@ -46,7 +46,7 @@ class PrintedpartsPlugin(BasePlugin):
         return printedparts_bp
 
     def get_models(self) -> List[Type]:
-        return [PrintedItem, PrintedItemTransaction]
+        return [PrintedItem, PrintedItemTransaction, PrintedItemFile]
 
     def init_app(self, app: Flask, db_instance) -> None:
         logger.info(f'Printedparts plugin initialized (v{self.meta.version})')
@@ -136,6 +136,9 @@ class PrintedpartsPlugin(BasePlugin):
             ('printedparts_alert_userids', '', 'string',
              'Comma-separated shopdb user ids whose account emails receive '
              'low-stock alerts'),
+            ('printedparts_alert_roleids', '', 'string',
+             'Comma-separated role ids; every active member of these roles '
+             'receives low-stock alerts'),
         ]
         for key, value, valuetype, description in defaults:
             if Setting.get(key) is None: