Housekeeping balance for Sharpe ratio and returns

[carkod]

We want to do a full revamp of balances so we can clearly see when we are making profit and how much risk and how efficient we are taking risk given the volatility.

• Balances is the endpoint currently used for PnL and the "Portfolio benchmarking" chart http://localhost:8008/account/balance-series
• We have multiple balances tables and deprecated/obsolete tables like staging and staging balance.
  • balances

                  id                  |   timestamp   | asset  |  quantity  | consolidated_balances_id 
-----------------------+-------------+------+----------+--------------------------
 647c1356-8baf-4880-8cf2-5c059938c328 | 1759253566993 | BTC   |   1.164e-05 |            1759253566993
 0dc920b6-9092-4803-a8a1-62d5f6640694 | 1759253566993 | NEO   |    4.121786 |            1759253566993
 02a680f9-99f2-42b1-bafb-6a544e28b872 | 1759253566993 | BNB   |    2.63e-06 |            1759253566993

consolidated balances

      id                 | estimated_total_fiat 
---------------+----------------------
 1759253566993 |             189.4308
 1753488064007 |             228.6742
 1753574464054 |             227.4141
 1753660864079 |             227.5513

Actions

• Current payload of /account/balance-series, "usdc" should be renamed to "fiat" since the capital used can vary depending on changing circumstances.

{
    "message": "Successfully retrieved balance series.",
    "error": 0,
    "data": {
        "usdc": [
            19.4353,
            17.7455,
           ....
        ],
        "btc": [
            65966.0,
            68438.71
        ],
        "dates": [
            1773014399999,
            1773100799999,
        ]
    }
}

• this endpoint is effectively returning the benchmark and the balance, so should be renamed to /account/portfolio/benchmark-series
• Calculate Sharpe ratio. AI prompt

• given that this data is being/going to be used in multiple places, add a new endpoint /account/portfolio/stats

"stats": {
  "last_pnl": float,
  "last_sharpe": float,
}

this should offload most of the logic that is currently done in front-end.