Let a bot take any colour

A bot's identity was one of seven hues, and the hue picked both its colour
and its stone shape. Now its colour is free and its stone is its own:

- `bots.color` holds any `#rrggbb`, `bots.stone` the flat-cut shape it's
  drawn on. `bots.hue` stays as the palette column they replaced, read only
  as a fallback; `src/scripts/move-bot-colour-to-owners.ts` backfills an
  install from it (safe to rerun).
- `src/utils/bot-color.ts` is the only place a colour is validated or
  resolved (`resolveBotColor`/`resolveBotStone` carry the old hue forward,
  `botColorNeedsPaperFace` flips the eyes to paper on a very dark body), and
  `src/utils/bot-stone-props.ts` gives every row its props, so a row saved
  before this still renders as it did.
- `BotStone` takes the colour as the body's SVG `fill`, the one documented
  exception to the token rule: an arbitrary hex has no token to point at.
  `UnreadDot` follows it.
- The picker keeps the palette tiles (still shape and colour together) and
  adds a native swatch and a hex field, so a custom colour keeps its stone.
  Same place as before: the header avatar's modal and Settings > Bots, for
  crew managers. The coordinator stays hue-less.
- A recolour reaches other open tabs through `pushBotUpdated`.

db/types/db.ts

@@ -189,7 +189,15 @@ export type BUN_SQLITE_COBBLE_BOTS = {
      */
     kind?: "worker" | "coordinator" | "";
     /** 
-     * Permanent identity hue. Null for the coordinator
+     * The bot's identity colour, a `#rrggbb` string. Null for the coordinator, which stays hue-less
+     */
+    color?: string;
+    /** 
+     * Which flat-cut stone the bot renders in its colour. The shape no longer follows the colour
+     */
+    stone?: "ember" | "amber" | "moss" | "teal" | "cobalt" | "violet" | "rose" | "";
+    /** 
+     * Historical: the palette hue from before `color` and `stone`. Only read as a fallback for a bot saved before them, and backfilled by `move-bot-colour-to-owners`
      */
     hue?: "ember" | "amber" | "moss" | "teal" | "cobalt" | "violet" | "rose" | "";
     /**