Remove dead legacy-import pipeline and unused LegacyAccount.password

The manual account-import flow made the old silent instance-import
pipeline unreachable. Drop the orphaned parsing, reachability checks,
batch import, result/error types, and the old import row view, plus the
httpClient dependency they were the only consumer of. Also remove the
LegacyAccount.password field, which was parsed but never read.

Yattee/Views/Settings/MigrationImportRow.swift

@@ -1,126 +0,0 @@
-//
-//  MigrationImportRow.swift
-//  Yattee
-//
-//  Reusable row component for displaying a legacy import item.
-//
-
-import SwiftUI
-
-struct MigrationImportRow: View {
-    let item: LegacyImportItem
-    let onToggle: () -> Void
-
-    var body: some View {
-        Button(action: onToggle) {
-            HStack(spacing: 12) {
-                // Checkbox
-                Image(systemName: item.isSelected ? "checkmark.circle.fill" : "circle")
-                    .font(.title2)
-                    .foregroundStyle(item.isSelected ? Color.accentColor : .secondary)
-
-                // Instance type icon
-                instanceIcon
-                    .font(.title2)
-                    .foregroundStyle(.secondary)
-                    .frame(width: 28)
-
-                // Instance details
-                VStack(alignment: .leading, spacing: 2) {
-                    Text(item.displayName)
-                        .font(.body)
-                        .foregroundStyle(.primary)
-
-                    Text(item.url.host ?? item.url.absoluteString)
-                        .font(.caption)
-                        .foregroundStyle(.secondary)
-                        .lineLimit(1)
-                }
-
-                Spacer()
-
-                // Reachability indicator
-                reachabilityIndicator
-            }
-            .padding(.vertical, 8)
-            .contentShape(Rectangle())
-        }
-        .buttonStyle(.plain)
-    }
-
-    // MARK: - Subviews
-
-    @ViewBuilder
-    private var instanceIcon: some View {
-        switch item.instanceType {
-        case .invidious:
-            Image(systemName: "server.rack")
-        case .piped:
-            Image(systemName: "cloud")
-        default:
-            Image(systemName: "globe")
-        }
-    }
-
-    @ViewBuilder
-    private var reachabilityIndicator: some View {
-        switch item.reachabilityStatus {
-        case .unknown:
-            EmptyView()
-        case .checking:
-            ProgressView()
-                .controlSize(.small)
-        case .reachable:
-            Image(systemName: "checkmark.circle.fill")
-                .foregroundStyle(.green)
-        case .unreachable:
-            Image(systemName: "exclamationmark.triangle.fill")
-                .foregroundStyle(.orange)
-        }
-    }
-}
-
-// MARK: - Preview
-
-#Preview {
-    List {
-        MigrationImportRow(
-            item: LegacyImportItem(
-                id: UUID(),
-                legacyInstanceID: "test",
-                instanceType: .invidious,
-                url: URL(string: "https://invidious.example.com")!,
-                name: "My Invidious",
-                isSelected: true,
-                reachabilityStatus: .reachable
-            ),
-            onToggle: {}
-        )
-
-        MigrationImportRow(
-            item: LegacyImportItem(
-                id: UUID(),
-                legacyInstanceID: "test2",
-                instanceType: .piped,
-                url: URL(string: "https://piped.example.com")!,
-                name: nil,
-                isSelected: false,
-                reachabilityStatus: .unreachable
-            ),
-            onToggle: {}
-        )
-
-        MigrationImportRow(
-            item: LegacyImportItem(
-                id: UUID(),
-                legacyInstanceID: "test3",
-                instanceType: .invidious,
-                url: URL(string: "https://another.invidious.com")!,
-                name: "Another Instance",
-                isSelected: true,
-                reachabilityStatus: .checking
-            ),
-            onToggle: {}
-        )
-    }
-}