chore: migrate all FA icons to Lucide (@lucide/svelte)

- Replaced all active FontAwesome <span class="fas fa-*"> icons with
  Lucide components across 145 files (excluding /idaa/ which is intentional)
- Fixed merge script bug: consolidated lucide-svelte imports into @lucide/svelte
- Replaced dynamic toggle patterns (fa-toggle-on/off) with ToggleRight/ToggleLeft
- Replaced fa-eye/fa-eye-slash with Eye/EyeOff
- Replaced fa-bug/fa-bug-slash with Bug/BugOff
- Replaced fa-sync fa-spin with RefreshCw + animate-spin
- Replaced fa-microchip with Cpu
- Fixed {@const} placement in element_manage_event_file_li.svelte
- Removed obsolete CSS hover rules for .unlock_icon/.lock_icon
- svelte-check: 0 errors, 0 warnings

documentation/TODO__Agents.md

@@ -84,7 +84,11 @@ Full audit: `src/routes/events/[event_id]/(leads)/` and `src/lib/ae_events/ae_ev
   omit from demo or hide the payment tab via "Show Payment Tab" toggle in Manage settings
 - [ ] **End-to-end smoke test** — sign in with shared passcode, scan/search a badge, add a lead,
   view detail, add notes/responses, export CSV; verify on mobile (Chrome/Safari PWA)
-- [ ] **Install prompt** — spec calls for a PWA install nudge on the Start tab; not yet added
+- [x] **Install prompt** — PWA install nudge implemented (2026-03-16). `pwa_install.svelte.ts`
+  singleton captures `beforeinstallprompt` (Chrome/Android/desktop) and detects iOS Safari
+  for manual "Share → Add to Home Screen" instructions. Reusable `element_pwa_install_prompt.svelte`
+  placed on the Leads Start tab between the feature grid and sign-in. `pwa_install.init()` wired
+  into root `+layout.svelte`; dismiss persists 7 days via localStorage. svelte-check: 0 errors.
 
 ### [DevOps] Remaining deployment items
 - [x] **Wire AE_APP_REPLICAS:** `docker-compose.yml` line 147 already has `scale: ${AE_APP_REPLICAS:-1}`. (verified 2026-03-11)