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/tests/test_auth.py

@@ -0,0 +1,40 @@
+"""Auth: login works, and protected/writer endpoints reject the wrong caller."""
+
+from tests.conftest import make_user
+from ten31portal.models import UserRole
+
+
+def test_login_success(client, approver):
+    resp = client.post(
+        "/api/auth/login", json={"login": "approver", "password": "password123"}
+    )
+    assert resp.status_code == 200, resp.text
+    assert resp.json()["username"] == "approver"
+
+
+def test_login_wrong_password(client, approver):
+    resp = client.post(
+        "/api/auth/login", json={"login": "approver", "password": "nope"}
+    )
+    assert resp.status_code == 401
+
+
+def test_me_requires_authentication(client):
+    assert client.get("/api/auth/me").status_code == 401
+
+
+def test_me_returns_current_user(auth_client):
+    resp = auth_client.get("/api/auth/me")
+    assert resp.status_code == 200
+    assert resp.json()["role"] == "approver"
+
+
+def test_writer_endpoint_rejects_viewer(client, session):
+    """A viewer is authenticated but not a writer — create-entity must 403, not 401."""
+    make_user(session, username="viewer", role=UserRole.viewer)
+    login = client.post(
+        "/api/auth/login", json={"login": "viewer", "password": "password123"}
+    )
+    assert login.status_code == 200
+    resp = client.post("/api/entities", json={"name": "X", "type": "fund"})
+    assert resp.status_code == 403