fix: real Xcode compile errors from Swift 6 strict concurrency

- SettingsView: ternary between .secondary (HierarchicalShapeStyle)
  and .red (Color) doesn't unify — both sides now explicit Color.
- CollectionRowView: passing OutlineIconMapping.sfSymbolName as a bare
  function reference to flatMap loses its (inferred default) MainActor
  isolation; wrapping it in a closure keeps the call inside body's
  already-MainActor context.
- NetworkMonitor: [weak self] was captured on NWPathMonitor's
  non-isolated pathUpdateHandler closure, which must cross into the
  inner @MainActor Task — moved the weak capture onto the Task closure
  itself instead, which is where it's actually used.

Outpost/Features/Account/SettingsView.swift

@@ -126,7 +126,7 @@ struct SettingsView: View {
                             if let lastFullSyncSummary {
                                 Text(fullSyncSummaryText(lastFullSyncSummary))
                                     .font(.caption)
-                                    .foregroundStyle(lastFullSyncSummary.errors.isEmpty ? .secondary : .red)
+                                    .foregroundStyle(lastFullSyncSummary.errors.isEmpty ? Color.secondary : Color.red)
                             }
                         }
                     }

Outpost/Features/Collections/CollectionRowView.swift

@@ -10,7 +10,7 @@ struct CollectionRowView: View {
         } icon: {
             if let emoji = collection.emojiIcon {
                 Text(emoji)
-            } else if let symbolName = collection.icon.flatMap(OutlineIconMapping.sfSymbolName) {
+            } else if let symbolName = collection.icon.flatMap({ OutlineIconMapping.sfSymbolName(for: $0) }) {
                 Image(systemName: symbolName)
                     .foregroundStyle(tintColor)
             } else {

Outpost/Support/NetworkMonitor.swift

@@ -14,9 +14,9 @@ final class NetworkMonitor {
     private let queue = DispatchQueue(label: "com.outpost.network-monitor")
 
     init() {
-        monitor.pathUpdateHandler = { [weak self] path in
+        monitor.pathUpdateHandler = { path in
             let online = path.status == .satisfied
-            Task { @MainActor in
+            Task { @MainActor [weak self] in
                 self?.isOnline = online
             }
         }