feat(app): remaining UI/UX improvements from Phase 2

[mschilling]

Context

Follow-up items from the Tab Restructuring & UX Improvements (Phase 2) work in PR #361. These are the remaining tasks that weren't included in the initial release.

Remaining Items

Medium Priority

• Empty states for new users — Show helpful messages when there's no data yet:
  • HQ: Welcome message with getting started hints when no daily progress / weekly stats
  • Activity Wall: "Start coding to see your activity here!" when "My Activity" filter has no results
  • Leaderboard: Encouraging message when no entries in a time period

Low Priority

• Activity pagination — Currently loads 100 activities at once. Increase limit and add "Load more" / infinite scroll for better UX on busy teams
• Edit profile button visibility — The edit pencil button on the profile page could be more prominent (larger tap target or text label)
• Profile header consistency — Align profile page header styling with other pages (HQ pattern)

Bug

• /users/:id route redirect — Navigating directly to /users/<id> redirects to / instead of showing the user profile. Likely a routing or auth guard issue.

Deferred

• Bottom nav badge counts — Requires notification center (see feat: in-app notification center #362)

Related

• PR feat(app): frontend UI/UX improvements #361 (merged) — Phase 2 main implementation
• Issue feat: in-app notification center #362 — In-app notification center
• Issue feat(app): add About & Community section to Settings page #363 — About & Community section in Settings