Add bot graphics

Bots can now show a concept as a visual: create_graphic (with
update_graphic, read_graphic and list_graphics, on every run, no computer
needed) stores one HTML document in bot_graphics, per user like the
conversation, and the chat renders its [graphic:ID] ref as an inline card
sized to fit, with a large view and a page of its own (no rail).

Graphic HTML is treated as hostile: it is only served at /graphics/<id>
with a CSP sandbox allowing scripts under an origin of its own and no
network, loading only the vendored Chart.js and Mermaid from
/graphics-lib/. The document carries the app's theme vars and scrollbars,
reports its height to the thread, and a frame that navigates away is
closed.

Co-Authored-By: Claude Opus 5.5 <[email protected]>

src/functions/backend/db/users/delete-user.ts

@@ -71,7 +71,7 @@ export default async function deleteUser({ actor_user_id, actor_user_types, user
     /**
      * These point at the user without a foreign key, so nothing cascades.
      */
-    for (const table of ["user_types", "user_passwords", "sso_login_codes", "secret_requests"]) {
+    for (const table of ["user_types", "user_passwords", "sso_login_codes", "secret_requests", "bot_graphics"]) {
         await BunSQLite.sql({ sql: `DELETE FROM ${table} WHERE user_id = ?`, values: [user.id] });
     }