chore(v2): restructure monorepo to src/ layout with uv

Aligns the repo with the python-project-spec-design.md template chosen
for V2.0.0. Big move, no logic changes. The 3 pre-existing test
failures (test_recipes::test_update_recipe, test_recipes::
test_recipe_versioning, test_tasks::test_reorder_tasks, plus the
client test_save_measurement_proxy) survive unchanged.

Layout changes
- server/        -> src/backend/
- server/middleware/ -> src/backend/api/middleware/
- server/routers/    -> src/backend/api/routers/
- server/models/     -> src/backend/models/orm/
- server/schemas/    -> src/backend/models/api/
- server/uploads/    -> uploads/ (project root, mounted volume)
- server/tests/      -> src/backend/tests/
- client/            -> src/frontend/flask_app/ (Flask kept; React
  deroga is documented in CLAUDE.md, justified by tablet UX, USB
  caliper/barcode workflow and Fabric.js integration)

Tooling
- pyproject.toml: monorepo with [project] core deps and
  optional-dependencies server / client / dev. Replaces both
  server/requirements.txt and client/requirements.txt.
- uv.lock + .python-version (3.11) committed for reproducible builds.
- Dockerfile (root, backend) and Dockerfile.frontend rewritten to use
  uv sync --frozen --no-dev --extra server|client; legacy Dockerfiles
  preserved as Dockerfile.legacy for reference but excluded from build
  context via .dockerignore.
- docker-compose.dev.yml + docker-compose.yml: build context now ".",
  dockerfile pointing to the root files.

Code adjustments forced by the move
- Every "from config|database|models|schemas|services|routers|middleware
  import ..." rewritten to its src.backend.* equivalent (50+ files
  including indented inline imports inside test bodies).
- src/backend/migrations/env.py: insert project root into sys.path so
  alembic can resolve src.backend.* imports regardless of cwd.
- src/backend/config.py: env_file ../../.env (was ../.env), upload_path
  resolves project root via parents[2].
- src/backend/tests/conftest.py + tests: import ... from src.backend.*
  instead of bare names; old per-directory pytest.ini files removed in
  favor of root pyproject.toml [tool.pytest.ini_options].
- .gitignore: uploads/ at root, src/frontend/flask_app/static/css/
  tailwind.css path; .dockerignore tightened.
- CLAUDE.md: rewrote sections "Layout del repository", "Comandi di
  Sviluppo", "Database & Migrations", "Test", "i18n", and all path
  references throughout the architecture sections.

Verified
- uv lock resolves 77 packages; uv sync --extra server --extra client
  --extra dev installs cleanly.
- uv run pytest: 171 passed, 4 pre-existing failures.
- uv run alembic -c src/backend/migrations/alembic.ini check loads
  config and metadata (errors only on the absent local MySQL).

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

src/backend/migrations/versions/001_add_image_path_to_recipe_and_subtask.py

@@ -0,0 +1,27 @@
+"""add image_path to recipe and subtask
+
+Revision ID: 001_image_path
+Revises:
+Create Date: 2026-02-20
+
+"""
+from typing import Sequence, Union
+
+from alembic import op
+import sqlalchemy as sa
+
+# revision identifiers, used by Alembic.
+revision: str = '001_image_path'
+down_revision: Union[str, None] = None
+branch_labels: Union[str, Sequence[str], None] = None
+depends_on: Union[str, Sequence[str], None] = None
+
+
+def upgrade() -> None:
+    op.add_column('recipes', sa.Column('image_path', sa.String(500), nullable=True))
+    op.add_column('recipe_subtasks', sa.Column('image_path', sa.String(500), nullable=True))
+
+
+def downgrade() -> None:
+    op.drop_column('recipe_subtasks', 'image_path')
+    op.drop_column('recipes', 'image_path')

src/backend/migrations/versions/002_add_stations.py

@@ -0,0 +1,53 @@
+"""add stations and station_recipe_assignments tables
+
+Revision ID: 002_add_stations
+Revises: 001_image_path
+Create Date: 2026-04-17
+
+"""
+from typing import Sequence, Union
+
+from alembic import op
+import sqlalchemy as sa
+
+revision: str = '002_add_stations'
+down_revision: Union[str, None] = '001_image_path'
+branch_labels: Union[str, Sequence[str], None] = None
+depends_on: Union[str, Sequence[str], None] = None
+
+
+def upgrade() -> None:
+    op.create_table(
+        'stations',
+        sa.Column('id', sa.Integer, primary_key=True, autoincrement=True),
+        sa.Column('code', sa.String(100), nullable=False),
+        sa.Column('name', sa.String(255), nullable=False),
+        sa.Column('location', sa.String(255), nullable=True),
+        sa.Column('notes', sa.Text, nullable=True),
+        sa.Column('active', sa.Boolean, nullable=False, server_default='1'),
+        sa.Column('created_by', sa.Integer, sa.ForeignKey('users.id'), nullable=False),
+        sa.Column('created_at', sa.DateTime, nullable=False, server_default=sa.func.now()),
+        sa.UniqueConstraint('code', name='uq_stations_code'),
+        sa.Index('ix_stations_active', 'active'),
+        mysql_engine='InnoDB',
+        mysql_charset='utf8mb4',
+    )
+
+    op.create_table(
+        'station_recipe_assignments',
+        sa.Column('id', sa.Integer, primary_key=True, autoincrement=True),
+        sa.Column('station_id', sa.Integer, sa.ForeignKey('stations.id', ondelete='CASCADE'), nullable=False),
+        sa.Column('recipe_id', sa.Integer, sa.ForeignKey('recipes.id', ondelete='CASCADE'), nullable=False),
+        sa.Column('assigned_by', sa.Integer, sa.ForeignKey('users.id'), nullable=False),
+        sa.Column('assigned_at', sa.DateTime, nullable=False, server_default=sa.func.now()),
+        sa.UniqueConstraint('station_id', 'recipe_id', name='uq_station_recipe'),
+        sa.Index('ix_sra_station', 'station_id'),
+        sa.Index('ix_sra_recipe', 'recipe_id'),
+        mysql_engine='InnoDB',
+        mysql_charset='utf8mb4',
+    )
+
+
+def downgrade() -> None:
+    op.drop_table('station_recipe_assignments')
+    op.drop_table('stations')