Convex-only Slice 1: clients talk to Convex, Flue is a private worker

Normalize the topology so web/desktop/mobile clients communicate only with
Convex. Convex admits durable commands, dispatches private Flue turns through
FLUE_URL, and stores the product-facing result before clients observe it.

- Normalized relational schema: organizations, projects, conversations/turns/
  messages/attachments, signals/sources/constraints, works/events/attachments.
- Conversation turns queued in Convex; the agent runAction dispatches to Flue
  and persists assistant response, signals, and proposed work back into Convex.
- Browser chat moved off the Flue transport: use-chat-agent now reads reactive
  Convex rows and sends through conversationMessages.send.
- Fixed signed-in blank screen: gate all product queries on useConvexAuth
  (isAuthenticated && !isRefreshing) plus personal-org bootstrap.
- Pinned react/react-dom to 19.2.8 via catalog to fix SSR dual-React crash.
- Removed ~16.6k net lines: daemon, AgentOS/Orb, project issues/runs/artifacts,
  todos, browser Flue transport, mobile execution views, smoke scripts.

Verified end-to-end on cheaptricks: connect repo, send actionable message,
Flue turn completes, Signal + proposed Work created with exact provenance,
persists across refresh.

packages/backend/convex/_generated/server.d.ts

@@ -26,6 +26,7 @@ import type { DataModel } from "./dataModel.js";
  */
 type Env = {
   readonly FLUE_DB_TOKEN: string;
+  readonly FLUE_URL: string | undefined;
   readonly GITEA_TOKEN: string | undefined;
   readonly GITEA_URL: string | undefined;
   readonly NATIVE_APP_URL: string | undefined;