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/config.py

@@ -5,3 +5,7 @@ import os
 
 DB_PATH: str = os.getenv("TEN31_DB_PATH", "/data/ten31portal/portal.db")
 SESSION_SECRET: str = os.getenv("TEN31_SESSION_SECRET", "change-me-in-production")
+DOCS_DIR: str = os.getenv("TEN31_DOCS_DIR", "/data/ten31portal/documents")
+# Cap on a single uploaded document. The docs dir shares the data volume with the DB, so an
+# unbounded upload could fill the disk and take the portal down. Default 50 MB.
+MAX_UPLOAD_SIZE: int = int(os.getenv("TEN31_MAX_UPLOAD_SIZE", str(50 * 1024 * 1024)))