Implement adjudicated DO items across backend, frontend, deploy

From the ROADMAP adjudication (12 of 13 DO items; D2 is a commit action).

Backend:
- B3: pytest suite (auth, entity CRUD, rollup) + dev deps + pytest config
- B4: cap document uploads at TEN31_MAX_UPLOAD_SIZE (default 50MB), stream-
  checked with partial-file cleanup, 413 on overflow
- B7: type AuditLog.detail as dict|list|str|None to match the JSON column
- B10: index foreign-key columns (migration a7b8c9d0e1f2 + index=True)
- B11: cli delete-user logs file-removal errors instead of swallowing them

Frontend:
- F2: distinguish "server unreachable" from "logged out"; retry prompt
- F4: confirm before destructive holdings-replace on import; step progress
- F6: expandable audit-log detail with full JSON
- F7: empty-state on the Investments page
- F8: shared role helpers (WRITER_ROLES/canEditRound/isApprover), used by
  EntitiesList, AuditLog, Import, ValuationWorkflow

Deploy:
- D5: run tsc --noEmit before packaging (build script)
- D6: TEN31_LOG_LEVEL env var (defaults to info)

Verified: 8/8 backend tests pass; alembic upgrades to head with 13 FK
indexes; upload limit rejects oversized + cleans up; frontend tsc + vite
build clean; dev server serves and proxies to the API.

backend/pyproject.toml

@@ -14,6 +14,13 @@ dependencies = [
     "aiosqlite==0.21.0",
     "starlette-session==0.4.3",
     "openpyxl==3.1.5",
+    "msoffcrypto-tool==6.0.0",
+]
+
+[project.optional-dependencies]
+dev = [
+    "pytest==8.3.4",
+    "httpx==0.28.1",  # required by starlette's TestClient
 ]
 
 [project.scripts]
@@ -23,3 +30,6 @@ ten31portal-cli = "ten31portal.cli:main"
 [build-system]
 requires = ["hatchling"]
 build-backend = "hatchling.build"
+
+[tool.pytest.ini_options]
+testpaths = ["tests"]