refactor: consolidate loading/error states and extract instance actions hook

Frontend:
- Create reusable DataStates components (LoadingState, ErrorState, EmptyState)
- Refactor 12 pages to use shared state components instead of inline JSX
- Extract useInstanceActions hook to eliminate session action duplication
- Update dashboard and sessions pages to use shared hook

OpenSpec:
- Archive completed mobile-app-usability change (44/44 tasks)
- Archive completed add-config-profiles change (15/15 tasks)

Quality: TypeScript check passes, production build succeeds

apps/web/src/pages/repo-workspace.tsx

@@ -1,4 +1,5 @@
 import { useCallback, useEffect, useState } from "react";
+import { EmptyState, ErrorState, LoadingState } from "../components/data-states";
 import { Icon } from "../components/icon";
 import { useMobileViewport } from "../hooks/use-mobile-viewport";
 
@@ -164,26 +165,16 @@ export const RepoWorkspace = () => {
       )}
 
       {status === "loading" && (
-        <p className="muted">Loading repositories...</p>
+        <LoadingState message="Loading repositories..." />
       )}
 
       {status === "error" && (
-        <div className="card stack">
-          <p>Failed to load repositories</p>
-          <button
-            className="secondary-button"
-            onClick={() => void loadRepositories()}
-            type="button"
-          >
-            <Icon name="refresh" size="sm" />
-            Retry
-          </button>
-        </div>
+        <ErrorState message="Failed to load repositories" onRetry={() => void loadRepositories()} />
       )}
 
       {status === "empty" && (
         <div className="card stack">
-          <p>No repositories in this project yet.</p>
+          <EmptyState message="No repositories in this project yet." />
           <Link
             className="primary-button"
             to={`/projects/${projectId}/settings/repositories`}
@@ -486,7 +477,7 @@ const FileBrowser = ({
         </button>
       )}
       {entries.length === 0 && (
-        <p className="muted">No files in this repository yet.</p>
+        <EmptyState message="No files in this repository yet." />
       )}
       {entries.map((entry) => {
         const fileStatus = entry.type === "file" ? getFileStatus(entry.path) : null;