0.2.39: bitcoin-denominated view, first-login flow, unfunded + tax center

- BTC prices: btc_prices table, CSV upload on Import page (auto-detected
  date/close columns, upsert by date), entities.close_date as the BTC entry
  mark; statements carry btc_price_cents (as-of) + btc_close_price_cents.
  LP capital blocks show paid-in vs current value in bitcoin terms.
- First login: accounts on the shared default password are flagged
  (must_change_password) and blocked behind a full-screen password change;
  external accounts then get a one-time welcome tour with a 2FA offer
  (users.onboarded_at).
- LP portal: Unfunded (callable commitment) metric; Tax documents center
  aggregating K-1/tax docs across funds, grouped by year.

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>

backend/ten31portal/cli.py

@@ -78,6 +78,7 @@ def reset_password(args: argparse.Namespace) -> None:
             sys.exit(1)
         user.password_hash = hash_password(args.password)
         user.login_enabled = True
+        user.must_change_password = False
         is_admin = user.is_service_admin
         session.add(user)
         session.commit()
@@ -134,6 +135,7 @@ def enable_investor_logins(args: argparse.Namespace) -> None:
         for u in users:
             u.password_hash = hash_password(config.DEFAULT_INVESTOR_PASSWORD)
             u.login_enabled = True
+            u.must_change_password = True
             session.add(u)
         session.commit()
         for u in users: