TOW-44: Hide RF Links UI elements from network map (#45)

## Summary

Hide RF link-related UI elements from the network map page while keeping all backend code intact.

### Changes
- Commented out "View RF Links" button in network map node detail panel
- Commented out RF Link health legend (Good signal / Degraded / Critical) from map legend
- Backend topology.ex code untouched — `compute_rf_link_stats/1` and `enrich_edges_with_rf/2` remain
- No RF tab exists on the device show page, so no changes needed there

### Verification
- `mix compile --warnings-as-errors` — zero warnings
- `mix test` — 8490 tests pass, 0 failures

Paperclip issue: TOW-44

Reviewed-on: graham/towerops-web#45

lib/towerops_web/live/network_map_live.html.heex

@@ -507,6 +507,7 @@
                     <.icon name="hero-arrow-top-right-on-square" class="h-4 w-4 mr-1.5" />
                     {t("View Device")}
                   </.link>
+                  <%!-- RF Links button hidden (TOW-44) — keep code intact
                   <%= if @selected_node_detail[:is_wireless] do %>
                     <.link
                       navigate={~p"/devices/#{@selected_node_detail.id}?tab=rf"}
@@ -516,6 +517,7 @@
                       {t("View RF Links")}
                     </.link>
                   <% end %>
+                  --%>
                 </div>
               <% end %>
             </div>
@@ -563,7 +565,7 @@
               <span class="text-gray-700 dark:text-gray-300">Discovered</span>
             </div>
           </div>
-          <%!-- RF Link health --%>
+          <%!-- RF Link health legend hidden (TOW-44) — keep code intact
           <div class="flex flex-wrap items-center gap-x-5 gap-y-1 text-xs">
             <span class="font-medium text-gray-600 dark:text-gray-400">RF Links:</span>
             <div class="flex items-center space-x-1.5">
@@ -579,6 +581,7 @@
               <span class="text-gray-700 dark:text-gray-300">Critical</span>
             </div>
           </div>
+          --%>
           <%!-- Link types --%>
           <div class="flex flex-wrap items-center gap-x-5 gap-y-1 text-xs">
             <span class="font-medium text-gray-600 dark:text-gray-400">Link types:</span>