feat(analytics): add portfolio rebalancing suggestions and health sco…

[shakourllahfashola-dev]

Closes #509

PR Description
Summary

This PR adds portfolio analytics capabilities to the propchain-analytics contract:

[get_rebalancing_suggestions(owner)](https://turbo-acorn-6976rp7vx6p9cxxxv.github.dev/)
[get_portfolio_health_score(owner)](https://turbo-acorn-6976rp7vx6p9cxxxv.github.dev/)

It enables owners to receive recommendation output and a 0-100 health score based on:

current allocation by property type
market trend signals per property type
diversification and concentration risk

What changed

Added new data types:
    [PortfolioPosition](https://turbo-acorn-6976rp7vx6p9cxxxv.github.dev/)
    RebalancingSuggestion
Added storage fields:
    portfolio_positions
    property_type_trends
Added contract methods:
    [set_portfolio_positions](https://turbo-acorn-6976rp7vx6p9cxxxv.github.dev/)
    [get_portfolio_positions](https://turbo-acorn-6976rp7vx6p9cxxxv.github.dev/)
    [update_property_type_trend](https://turbo-acorn-6976rp7vx6p9cxxxv.github.dev/)
    [get_property_type_trend](https://turbo-acorn-6976rp7vx6p9cxxxv.github.dev/)
    [get_rebalancing_suggestions](https://turbo-acorn-6976rp7vx6p9cxxxv.github.dev/)
    [get_portfolio_health_score](https://turbo-acorn-6976rp7vx6p9cxxxv.github.dev/)
Added tests validating:
    low health score for a concentrated portfolio
    high(er) health score for a diversified portfolio
    rebalancing suggestions updating when market trends shift

Files changed

[lib.rs](https://turbo-acorn-6976rp7vx6p9cxxxv.github.dev/)

[drips-wave]

@shakourllahfashola-dev Great news! 🎉 Based on an automated assessment of this PR, the linked Wave issue(s) no longer count against your application limits.

You can now already apply to more issues while waiting for a review of this PR. Keep up the great work! 🚀

Learn more about application limits