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/tests/test_reports.py

@@ -0,0 +1,107 @@
+"""Tests for reports router (/api/reports).
+
+Note: Report generation requires WeasyPrint/Kaleido and Jinja2 templates.
+These tests mock the PDF generation to test endpoint plumbing and auth.
+"""
+from unittest.mock import AsyncMock, patch
+
+import pytest
+from httpx import AsyncClient
+from sqlalchemy.ext.asyncio import AsyncSession
+
+from src.backend.models.orm.user import User
+from src.backend.tests.conftest import auth_headers, create_test_recipe
+
+
+class TestMeasurementReport:
+    """GET /api/reports/measurements tests."""
+
+    async def test_generate_measurement_report(
+        self,
+        client: AsyncClient,
+        metrologist_user: User,
+        db_session: AsyncSession,
+    ):
+        """Metrologist can generate a measurement report (mocked PDF)."""
+        recipe = await create_test_recipe(
+            db_session, metrologist_user.id
+        )
+
+        fake_pdf = b"%PDF-1.4 fake content"
+        with patch(
+            "src.backend.api.routers.reports.generate_measurement_report",
+            new_callable=AsyncMock,
+            return_value=fake_pdf,
+        ):
+            resp = await client.get(
+                "/api/reports/measurements",
+                headers=auth_headers(metrologist_user),
+                params={"recipe_id": recipe.id},
+            )
+
+        assert resp.status_code == 200
+        assert resp.headers["content-type"] == "application/pdf"
+        assert b"%PDF" in resp.content
+
+    async def test_report_requires_auth(self, client: AsyncClient):
+        """Report endpoints require authentication."""
+        resp = await client.get(
+            "/api/reports/measurements",
+            params={"recipe_id": 1},
+        )
+        assert resp.status_code == 401
+
+
+class TestSPCReport:
+    """GET /api/reports/spc tests."""
+
+    async def test_generate_spc_report(
+        self,
+        client: AsyncClient,
+        metrologist_user: User,
+        db_session: AsyncSession,
+    ):
+        """Metrologist can generate an SPC report (mocked PDF)."""
+        recipe = await create_test_recipe(
+            db_session, metrologist_user.id
+        )
+
+        # Get subtask_id
+        tasks_resp = await client.get(
+            f"/api/recipes/{recipe.id}/tasks",
+            headers=auth_headers(metrologist_user),
+        )
+        subtask_id = tasks_resp.json()[0]["subtasks"][0]["id"]
+
+        fake_pdf = b"%PDF-1.4 spc report content"
+        with patch(
+            "src.backend.api.routers.reports.generate_spc_report",
+            new_callable=AsyncMock,
+            return_value=fake_pdf,
+        ):
+            resp = await client.get(
+                "/api/reports/spc",
+                headers=auth_headers(metrologist_user),
+                params={
+                    "recipe_id": recipe.id,
+                    "subtask_id": subtask_id,
+                },
+            )
+
+        assert resp.status_code == 200
+        assert resp.headers["content-type"] == "application/pdf"
+
+    async def test_spc_report_requires_metrologist(
+        self,
+        client: AsyncClient,
+        maker_user: User,
+        db_session: AsyncSession,
+    ):
+        """Non-Metrologist cannot generate SPC reports."""
+        recipe = await create_test_recipe(db_session, maker_user.id)
+        resp = await client.get(
+            "/api/reports/spc",
+            headers=auth_headers(maker_user),
+            params={"recipe_id": recipe.id, "subtask_id": 1},
+        )
+        assert resp.status_code == 403