Documentation hub at /docs — one place to find everything

If you typed /docs into the address bar on quantistrade.co.uk, you used to get a 404. That was embarrassing — somebody we'd just promoted the platform to went looking for it and bounced. Fixed.

/docs is now a documentation hub: five sections of plain-English links into the rest of the site. Start here, core metrics (Sharpe, Sortino, Calmar, MAR, max drawdown, hit rate, turnover, alpha, beta, information ratio), concepts that show up across the platform (overfitting, Sharpe vs PSR vs DSR, walk-forward vs CPCV, factor decomposition, IC decay), strategy types the natural-language agent recognises (momentum, mean reversion, quality, low volatility), and the usual contact / security shortcuts.

Each entry is one short blurb that links into deeper material in the Learning Centre or to the contact page. The point is to give somebody who's never used the platform a single place to land that doesn't dump them straight into the dashboard.

While shipping this we also fixed a build-time issue where the changelog loader was reading from docs/changelog/ but the Dockerfile wasn't copying that directory into the image. That's why an unrelated catastrophic restart earlier today briefly took /changelog offline along with /docs. Both are now baked into the image and won't regress on the next rebuild.