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/git-mount-editor.tsx

@@ -1,5 +1,5 @@
 import { useState, useEffect } from "react";
-import { Icon } from "./icon";
+import { Icon } from "@/components/ui/Icon";
 import { validateGitUrl } from "../api/config_profiles";
 import type { GitMount, GitMountMapping } from "../api/config_profiles";