Individual/separate story pages

Have a separate/individual story page for each company. Right now there is only a single global story page that also shows up as a individual one, but in reality there is only one story page.

This would allow:
- The "You have completed the objective and won the game!" text to properly show up for each company when they win. Right now it only shows in single player and it shows for all companies (AIs)
- The goals listed on the story page to link to the company's goal window when clicked on
- The story page for each company to show independently when they join. Right now, the story page only shows in single player when you start a game.

The issue names no files, tests, or entry points; begin by locating the existing global story-page implementation and the company, join, and win UI paths. Done means each company has an independent story page, its goals link to that company's goal window, win text is company-specific, and the page appears when companies join.

Written by the indexing model from the issue text.