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/services/measurement_service.py

@@ -0,0 +1,77 @@
+"""Measurement service - pass/fail calculation, data storage."""
+from decimal import Decimal
+
+from sqlalchemy import select
+from sqlalchemy.ext.asyncio import AsyncSession
+
+from src.backend.models.orm.measurement import Measurement
+from src.backend.models.orm.task import RecipeSubtask
+
+
+def calculate_pass_fail(
+    value: float, subtask: RecipeSubtask
+) -> tuple[str, float | None]:
+    """Calculate pass/fail status and deviation based on tolerances.
+
+    Returns (status, deviation) where status is 'pass', 'warning', or 'fail'.
+
+    Logic:
+    - If value is outside UTL/LTL -> 'fail'
+    - If value is outside UWL/LWL but inside UTL/LTL -> 'warning'
+    - Otherwise -> 'pass'
+    """
+    deviation = None
+    if subtask.nominal is not None:
+        deviation = float(Decimal(str(value)) - Decimal(str(subtask.nominal)))
+
+    # Check fail (outside tolerance limits)
+    if subtask.utl is not None and value > float(subtask.utl):
+        return "fail", deviation
+    if subtask.ltl is not None and value < float(subtask.ltl):
+        return "fail", deviation
+
+    # Check warning (outside warning limits)
+    if subtask.uwl is not None and value > float(subtask.uwl):
+        return "warning", deviation
+    if subtask.lwl is not None and value < float(subtask.lwl):
+        return "warning", deviation
+
+    return "pass", deviation
+
+
+async def save_measurement(
+    db: AsyncSession,
+    subtask_id: int,
+    version_id: int,
+    measured_by: int,
+    value: float,
+    lot_number: str | None = None,
+    serial_number: str | None = None,
+    input_method: str = "manual",
+) -> Measurement:
+    """Save a single measurement with auto-calculated pass/fail."""
+    # Get subtask for tolerance values
+    result = await db.execute(
+        select(RecipeSubtask).where(RecipeSubtask.id == subtask_id)
+    )
+    subtask = result.scalar_one_or_none()
+    if subtask is None:
+        raise ValueError(f"Subtask {subtask_id} not found")
+
+    pass_fail, deviation = calculate_pass_fail(value, subtask)
+
+    measurement = Measurement(
+        subtask_id=subtask_id,
+        version_id=version_id,
+        measured_by=measured_by,
+        value=value,
+        pass_fail=pass_fail,
+        deviation=deviation,
+        lot_number=lot_number,
+        serial_number=serial_number,
+        input_method=input_method,
+    )
+    db.add(measurement)
+    await db.flush()
+    await db.refresh(measurement)
+    return measurement