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/frontend/flask_app/tests/test_statistics.py

@@ -0,0 +1,88 @@
+"""Tests for statistics blueprint (client/blueprints/statistics.py).
+
+Covers dashboard rendering, role enforcement, and SPC/summary API proxies.
+"""
+import pytest
+
+
+class TestDashboard:
+    """GET /statistics/dashboard tests."""
+
+    def test_dashboard_renders(self, logged_in_client, mock_api_client):
+        """Dashboard renders for Metrologist role."""
+        mock_api_client.get.return_value = {
+            "items": [
+                {"id": 1, "code": "REC-001", "name": "Recipe A"},
+            ],
+            "total": 1,
+            "pages": 1,
+        }
+
+        resp = logged_in_client.get("/statistics/dashboard")
+        assert resp.status_code == 200
+
+    def test_dashboard_requires_login(self, client):
+        """Unauthenticated user is redirected to login."""
+        resp = client.get("/statistics/dashboard", follow_redirects=False)
+        assert resp.status_code == 302
+        assert "/auth/login" in resp.headers["Location"]
+
+
+class TestRoleRequired:
+    """Metrologist role enforcement tests."""
+
+    def test_requires_metrologist_role(self, flask_app):
+        """User without Metrologist role gets 403 on statistics endpoints."""
+        with flask_app.test_client() as c:
+            with c.session_transaction() as sess:
+                sess["api_key"] = "test-key"
+                sess["user"] = {
+                    "id": 3,
+                    "username": "maker_only",
+                    "display_name": "Maker Only",
+                    "roles": ["Maker"],
+                    "is_admin": False,
+                    "language_pref": "en",
+                    "theme_pref": "light",
+                    "active": True,
+                }
+                sess["user_id"] = 3
+                sess["language"] = "en"
+                sess["theme"] = "light"
+
+            resp = c.get("/statistics/dashboard")
+            assert resp.status_code == 403
+
+
+class TestSPCProxy:
+    """SPC data proxy endpoint tests."""
+
+    def test_summary_proxy(self, logged_in_client, mock_api_client):
+        """Summary API proxy returns JSON from backend."""
+        mock_api_client.get.return_value = {
+            "total": 100,
+            "pass_count": 90,
+            "fail_count": 5,
+            "warning_count": 5,
+        }
+
+        resp = logged_in_client.get(
+            "/statistics/api/summary?recipe_id=1"
+        )
+        assert resp.status_code == 200
+        data = resp.get_json()
+        assert data["total"] == 100
+
+    def test_capability_proxy(self, logged_in_client, mock_api_client):
+        """Capability API proxy returns JSON from backend."""
+        mock_api_client.get.return_value = {
+            "cp": 1.33,
+            "cpk": 1.20,
+        }
+
+        resp = logged_in_client.get(
+            "/statistics/api/capability?recipe_id=1&subtask_id=1"
+        )
+        assert resp.status_code == 200
+        data = resp.get_json()
+        assert "cp" in data