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/profile.tsx

@@ -1,6 +1,7 @@
 import { useCallback, useEffect, useRef, useState } from "react";
 
 import { getProfile, updateProfile, uploadAvatar } from "../api/profile";
+import { EmptyState, ErrorState, LoadingState } from "../components/data-states";
 import { Icon } from "../components/icon";
 import { useAuth } from "../state/auth";
 import { useAsyncData } from "../hooks/use-async-data";
@@ -91,17 +92,9 @@ export const ProfilePage = () => {
     <section className="stack">
       <h1>Profile</h1>
 
-      {displayStatus === "loading" && <p className="muted">Loading profile...</p>}
+      {displayStatus === "loading" && <LoadingState message="Loading profile..." />}
 
-      {displayStatus === "error" && (
-        <div className="card stack">
-          <p>Failed to load profile</p>
-          <button className="secondary-button" onClick={() => reload()} type="button">
-            <Icon name="refresh" size="sm" />
-            Retry
-          </button>
-        </div>
-      )}
+      {displayStatus === "error" && <ErrorState message="Failed to load profile" onRetry={reload} />}
 
       {(displayStatus === "ready" || displayStatus === "saving") && profile && (
         <div className="card stack">