v0.151.0 — Bert M2: Bert does things

The Bert program's second milestone: Bert can change things for you. Small changes you ask for happen at once, as you, each marked via Bert in History, and Undo takes a turn's changes back together. Anything that deletes, or that you didn't ask for in your own words, waits for Do it. The program's documents are in docs/programs/bert/; this milestone's tasks, decisions and test script are in docs/programs/bert/m2-bert-does-things.md.

• [x] Bert does small things you ask for: set a token's HP or another property, add or remove a condition, move a token by squares, rename a map or a token, say something in chat as you. Each is done as you, through the same routes and permissions, marked via Bert in history, and the reply's Undo takes the turn's changes back together (never someone else's later edit, and never what you may no longer change).
• [x] Bigger things wait for Do it: deleting a token, a drawing, a placed Object, an aura, action or artwork, resetting the fog of war, and generating monsters or an encounter to place near a token, are proposed with what they will change, and nothing happens until you tap Do it (or Cancel). A change Bert wasn't asked for in your own words, such as one suggested by something it read, is only proposed too.
• [x] Which map has the werewolf? Bert finds tokens across a campaign's maps by name or by who made them.
• [x] Links in chat: a URL anyone writes is a link (http and https only), and chat messages are now sanitised before they're shown.
• [x] Bert's words become buttons: when an answer sends you to Settings → AI → Assistant, a help page, Campaigns or the Library, the reply has a button that opens it; the no-key reply opens Settings at the right place.
• [x] The chat box is no longer a form field: LastPass kept putting its icon in it through every opt-out, so it's now an editable area with nothing for a password manager to fill. It looks and works as before: Enter sends, Up recalls, /w suggests, and pasted line breaks become spaces.