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/migrations/versions/0002_printeditemfiles.py

@@ -0,0 +1,43 @@
+"""Add printeditemfiles: append-only print-file revisions per item.
+
+The plugin's first incremental migration on top of its 0001 baseline -
+the ADR-008 payoff: the plugin evolves its own schema without touching
+the core chain. Applied by `flask plugin upgrade-all`.
+"""
+from alembic import op
+import sqlalchemy as sa
+
+
+# revision identifiers, used by Alembic.
+revision = 'printedparts0002files'
+down_revision = 'printedparts0001baseline'
+branch_labels = None
+depends_on = None
+
+
+def upgrade():
+    op.create_table(
+        'printeditemfiles',
+        sa.Column('fileid', sa.Integer(), nullable=False),
+        sa.Column('printeditemid', sa.Integer(), nullable=False),
+        sa.Column('revision', sa.Integer(), nullable=False),
+        sa.Column('filename', sa.String(length=255), nullable=False),
+        sa.Column('storedfilename', sa.String(length=191), nullable=False),
+        sa.Column('filesize', sa.Integer(), nullable=False),
+        sa.Column('uploadnote', sa.String(length=255), nullable=True),
+        sa.Column('uploadedby', sa.String(length=80), nullable=False),
+        sa.Column('createddate', sa.DateTime(), nullable=False),
+        sa.Column('modifieddate', sa.DateTime(), nullable=False),
+        sa.Column('isactive', sa.Boolean(), nullable=False),
+        sa.ForeignKeyConstraint(['printeditemid'],
+                                ['printeditems.printeditemid'],
+                                ondelete='CASCADE'),
+        sa.PrimaryKeyConstraint('fileid'),
+        sa.UniqueConstraint('storedfilename'),
+    )
+    op.create_index('ix_printeditemfiles_printeditemid',
+                    'printeditemfiles', ['printeditemid'])
+
+
+def downgrade():
+    op.drop_table('printeditemfiles')