merge: integrate main restructuring into dev

- Resolve 57 merge conflicts from codebase restructure
- Port dev feature code to new directory structure:
  * Update import paths to use @/ aliases
  * Add backward-compatible API signatures (createInstance, startInstance, deleteInstance)
  * Add missing type exports (ProjectWithRepos, InstanceHealth, Branch, BranchesResponse)
  * Extend Session and GitRepository types for dev features
  * Extend TerminalComponent props for mobile terminal wrapper
  * Add missing icon names (bell, drag, undo)

Quality gates: tsc pass (0 errors), build pass, 127/131 tests pass
(4 pre-existing failures unrelated to merge)

apps/web/src/components/start-tool-fab.tsx

@@ -1,7 +1,7 @@
 /** Floating action button to start a tool from any page. */
 
 import { useState } from "react";
-import { Icon } from "./icon";
+import { Icon } from "@/components/ui/Icon";
 import { ToolStarter } from "./tool-starter";
 import type { Workspace } from "../types/workspace";
 import { listAllWorkspaces } from "../api/workspaces";