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/models/api/measurement.py

@@ -0,0 +1,62 @@
+"""Pydantic schemas for Measurement operations."""
+from datetime import datetime
+from typing import Optional
+
+from pydantic import BaseModel, ConfigDict, Field
+
+
+class MeasurementCreate(BaseModel):
+    """Schema for creating a single measurement."""
+    subtask_id: int
+    version_id: int
+    value: float
+    lot_number: Optional[str] = Field(None, max_length=100)
+    serial_number: Optional[str] = Field(None, max_length=100)
+    input_method: str = Field("manual", pattern="^(usb_caliper|manual)$")
+
+
+class MeasurementBatchCreate(BaseModel):
+    """Schema for creating multiple measurements at once."""
+    measurements: list[MeasurementCreate]
+
+
+class MeasurementResponse(BaseModel):
+    """Schema for measurement response."""
+    model_config = ConfigDict(from_attributes=True)
+
+    id: int
+    subtask_id: int
+    version_id: int
+    measured_by: int
+    value: float
+    pass_fail: str
+    deviation: Optional[float] = None
+    lot_number: Optional[str] = None
+    serial_number: Optional[str] = None
+    input_method: str
+    measured_at: datetime
+    synced_to_csv: bool
+
+
+class MeasurementListResponse(BaseModel):
+    """Schema for paginated measurement list."""
+    items: list[MeasurementResponse]
+    total: int
+    page: int
+    per_page: int
+    pages: int
+
+
+class MeasurementQuery(BaseModel):
+    """Schema for measurement query filters."""
+    recipe_id: Optional[int] = None
+    version_id: Optional[int] = None
+    subtask_id: Optional[int] = None
+    measured_by: Optional[int] = None
+    lot_number: Optional[str] = None
+    serial_number: Optional[str] = None
+    date_from: Optional[datetime] = None
+    date_to: Optional[datetime] = None
+    pass_fail: Optional[str] = Field(None, pattern="^(pass|warning|fail)$")
+    page: int = Field(1, ge=1)
+    per_page: int = Field(50, ge=1, le=500)