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/ten31portal/storage.py

@@ -0,0 +1,62 @@
+"""File storage on the data volume for uploaded documents."""
+
+import os
+import shutil
+from pathlib import Path
+from uuid import uuid4
+
+from fastapi import UploadFile
+
+from ten31portal.config import DOCS_DIR, MAX_UPLOAD_SIZE
+
+
+class UploadTooLarge(Exception):
+    """Raised when an upload exceeds MAX_UPLOAD_SIZE. The partial file is removed first."""
+
+
+def ensure_docs_dir() -> Path:
+    path = Path(DOCS_DIR)
+    path.mkdir(parents=True, exist_ok=True)
+    return path
+
+
+def save_upload(file: UploadFile) -> tuple[str, int]:
+    """Stream an upload to disk under an opaque name. Returns (storage_path, size_bytes).
+
+    Enforces MAX_UPLOAD_SIZE as it streams so a runaway upload can't fill the data volume;
+    the partial file is deleted before UploadTooLarge propagates.
+    """
+    docs = ensure_docs_dir()
+    suffix = Path(file.filename or "").suffix
+    storage_name = f"{uuid4().hex}{suffix}"
+    dest = docs / storage_name
+    size = 0
+    try:
+        with dest.open("wb") as out:
+            while chunk := file.file.read(1024 * 1024):
+                size += len(chunk)
+                if size > MAX_UPLOAD_SIZE:
+                    raise UploadTooLarge(
+                        f"Upload exceeds the {MAX_UPLOAD_SIZE}-byte limit."
+                    )
+                out.write(chunk)
+    except UploadTooLarge:
+        dest.unlink(missing_ok=True)
+        raise
+    return storage_name, size
+
+
+def full_path(storage_path: str) -> Path:
+    """Resolve a stored file, guarding against path traversal."""
+    docs = ensure_docs_dir().resolve()
+    candidate = (docs / storage_path).resolve()
+    if not str(candidate).startswith(str(docs) + os.sep):
+        raise ValueError("Invalid storage path")
+    return candidate
+
+
+def delete_file(storage_path: str) -> None:
+    try:
+        full_path(storage_path).unlink(missing_ok=True)
+    except ValueError:
+        pass