Starred bots, bot limits by plan, and source fixes.

New: Star bots on the dashboard and choose the sort order of the bot list.
Improved: The number of bots you can create follows your plan.
Fixed: "Your bot is still processing training sources" sometimes stayed on screen after training finished.
Fixed: Adding a URL you had already added was rejected; rescanning and re-adding URL sources was reworked.
Fixed: Occasional sign-in errors when opening dashboard pages directly.