Keep every weekly quota window and page through them

[czpython]

A plan can meter one model's weekly quota separately from the rest. The parser kept only the window closest to exhaustion and discarded the others, so once that model ran out the weekly meter pinned to its 0% with nothing to roll over to — and the panel announced the whole harness was out when only one model was.

Every weekly window a plan reports is now kept end to end. usage_scrapes stores them as one ordered list, /usage returns all of them, and /usage/history returns a series per window. The weekly row becomes a carousel: it opens on the window that binds, and dots show the operator there are others — one of which may still have room.

The exhaustion banner scopes its warning. An unscoped window at 0% still means new runs on that harness will fail; a window metered to one model says so, and names the model.

The five-hour meter is unchanged: singular, unscoped, fixed above the weekly row.

Migration b6d9e2c4f8a1 folds the three week_* columns into weeks and reverses.

Closes ENG-809.