Improve ice-sovler to take trade weight into account.

Currently, solver can produce solutions where it only has constant limits for a solution - max 100 intents, and max 30 trades.

in the worst possible scenario - scenario with 30 9-hop trades would be rejected as overweight ( but currently not really possible to make solver produces such solution ).

But it would be nice to have solver to consider and take into account also weight of each trade and given max solution weight - it produces solution that would fit comfortably every time.

Start by locating the ice-solver implementation and how it enforces the current 100-intent and 30-trade limits. Trace how each trade's weight and the maximum solution weight are represented, then verify that generated solutions stay within the requested weight while preserving the existing limits.

Written by the indexing model from the issue text.