Add the measuringtools plugin (ADR-005) and the plugin-system tutorial

Gage-lab instruments as Asset extensions: measuringtooltypes (color-coded
lookup) + measuringtools (calibration interval/dates, provider, notes) with
calibration status derived at read time (overdue / due soon / current /
unknown), never stored. Full CRUD API with permission-gated writes, types
management with in-use guard, calibration report, nav/reports/config-schema
hooks, and a complete frontend (list/detail/form, types settings page,
calibration report page, gated routes per ADR-009).

First plugin whose migration chain really creates tables post-cutover
(ADR-008), and the working example for docs/PLUGIN-GUIDE.md - a 12-section
walkthrough of building a plugin on this framework, linked from
PLUGIN-QUICKSTART and PLUGINS.

Verified: full suite 323 passing, live E2E on all four pages, fresh
scratch-MySQL migration dry-run green.

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>

plugins/measuringtools/migrations/versions/0001_measuringtools_baseline.py

@@ -0,0 +1,69 @@
+"""measuringtools plugin baseline (real create).
+
+This plugin was built AFTER the ADR-008 ownership cutover, so unlike the ten
+bundled plugins whose 0001 is a stamp-only no-op anchor, this baseline actually
+CREATES the plugin's tables. The core Alembic chain never knew about
+measuringtooltypes / measuringtools, so this per-plugin chain is their sole
+authoritative creator. It runs from `flask plugin install measuringtools`
+(and `flask plugin upgrade-all`) after `flask db upgrade` builds the core schema.
+
+Note on create_plugin_tables: the shared helper in
+shopdb.plugins.alembic_template builds a per-plugin MetaData filtered to only the
+plugin's own tables, which means a foreign key to a core table (assets) cannot
+be resolved at CreateTable-compile time (NoReferencedTableError). Since these
+tables reference assets.assetid, the baseline emits explicit Alembic ops (the
+same shape Alembic autogenerate produces) instead. Tables inherit the
+connection's default charset, so on a utf8mb4 database they are utf8mb4, matching
+how the core chain creates its tables.
+"""
+from alembic import op
+import sqlalchemy as sa
+
+
+# revision identifiers, used by Alembic.
+revision = 'measuringtools0001baseline'
+down_revision = None
+branch_labels = None
+depends_on = None
+
+
+def upgrade():
+    op.create_table(
+        'measuringtooltypes',
+        sa.Column('measuringtooltypeid', sa.Integer(), nullable=False),
+        sa.Column('name', sa.String(length=100), nullable=False),
+        sa.Column('description', sa.Text(), nullable=True),
+        sa.Column('color', sa.String(length=20), nullable=True),
+        sa.Column('createddate', sa.DateTime(), nullable=False),
+        sa.Column('modifieddate', sa.DateTime(), nullable=False),
+        sa.Column('isactive', sa.Boolean(), nullable=False),
+        sa.PrimaryKeyConstraint('measuringtooltypeid'),
+        sa.UniqueConstraint('name'),
+    )
+    op.create_table(
+        'measuringtools',
+        sa.Column('measuringtoolid', sa.Integer(), nullable=False),
+        sa.Column('assetid', sa.Integer(), nullable=False),
+        sa.Column('measuringtooltypeid', sa.Integer(), nullable=True),
+        sa.Column('calibrationintervaldays', sa.Integer(), nullable=True),
+        sa.Column('lastcalibrationdate', sa.Date(), nullable=True),
+        sa.Column('nextcalibrationdate', sa.Date(), nullable=True),
+        sa.Column('calibrationprovider', sa.String(length=150), nullable=True),
+        sa.Column('notes', sa.Text(), nullable=True),
+        sa.Column('createddate', sa.DateTime(), nullable=False),
+        sa.Column('modifieddate', sa.DateTime(), nullable=False),
+        sa.Column('isactive', sa.Boolean(), nullable=False),
+        sa.ForeignKeyConstraint(['assetid'], ['assets.assetid'], ondelete='CASCADE'),
+        sa.ForeignKeyConstraint(['measuringtooltypeid'],
+                                ['measuringtooltypes.measuringtooltypeid']),
+        sa.PrimaryKeyConstraint('measuringtoolid'),
+        sa.UniqueConstraint('assetid'),
+    )
+    op.create_index('idx_measuringtool_type', 'measuringtools',
+                    ['measuringtooltypeid'])
+
+
+def downgrade():
+    op.drop_index('idx_measuringtool_type', table_name='measuringtools')
+    op.drop_table('measuringtools')
+    op.drop_table('measuringtooltypes')