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/statistics.py

@@ -0,0 +1,94 @@
+"""Pydantic schemas for SPC statistics responses."""
+from datetime import datetime
+from typing import Optional
+
+from pydantic import BaseModel, Field
+
+
+class StatisticsQuery(BaseModel):
+    """Common query parameters for statistics endpoints."""
+    recipe_id: int
+    version_id: Optional[int] = None
+    subtask_id: Optional[int] = None
+    date_from: Optional[datetime] = None
+    date_to: Optional[datetime] = None
+    operator_id: Optional[int] = None
+    lot_number: Optional[str] = None
+    serial_number: Optional[str] = None
+
+
+class ControlChartData(BaseModel):
+    """Data for X-bar/R control chart."""
+    values: list[float]
+    timestamps: list[datetime]
+    mean: float
+    ucl: float  # Upper Control Limit
+    lcl: float  # Lower Control Limit
+    utl: Optional[float] = None
+    uwl: Optional[float] = None
+    lwl: Optional[float] = None
+    ltl: Optional[float] = None
+    nominal: Optional[float] = None
+    out_of_control: list[int] = []  # Indices of OOC points
+
+
+class HistogramData(BaseModel):
+    """Data for histogram with normal curve."""
+    bins: list[float]
+    counts: list[int]
+    normal_x: list[float]
+    normal_y: list[float]
+    mean: float
+    std_dev: float
+    n: int
+
+
+class CapabilityData(BaseModel):
+    """Capability indices."""
+    cp: Optional[float] = None
+    cpk: Optional[float] = None
+    pp: Optional[float] = None
+    ppk: Optional[float] = None
+    mean: float
+    std_dev: float
+    n: int
+    utl: Optional[float] = None
+    ltl: Optional[float] = None
+    nominal: Optional[float] = None
+
+
+class TrendData(BaseModel):
+    """Temporal trend data for capability indices."""
+    dates: list[datetime]
+    cpk_values: list[Optional[float]]
+    ppk_values: list[Optional[float]]
+    n_per_period: list[int]
+
+
+class SummaryData(BaseModel):
+    """Pass/fail/warning summary counts."""
+    total: int
+    pass_count: int
+    warning_count: int
+    fail_count: int
+    pass_rate: float
+    warning_rate: float
+    fail_rate: float
+
+
+class AlertData(BaseModel):
+    """Western Electric rules violations."""
+    rule: str
+    description: str
+    points: list[int]  # Indices of violating points
+    severity: str = Field(..., pattern="^(info|warning|critical)$")
+
+
+class StatisticsResponse(BaseModel):
+    """Combined statistics response."""
+    summary: SummaryData
+    capability: Optional[CapabilityData] = None
+    control_chart: Optional[ControlChartData] = None
+    histogram: Optional[HistogramData] = None
+    trend: Optional[TrendData] = None
+    alerts: list[AlertData] = []