Refactor certificate fetching and validation logic

Refactor OfficialCertsDownloader to improve certificate fetching logic and add validation for required files.

Author: NovaDev404

Sources/prostore/certificates/OfficialCertsDownloader.swift

@@ -163,26 +163,44 @@ struct OfficialCertificatesView: View {
             .font(.caption)
     }
 
-    private func fetchTrees() {
-        Task {
-            let url = URL(string: "https://api.github.com/repos/ProStore-iOS/certificates/git/trees/main")!
-            do {
-                let (data, _) = try await URLSession.shared.data(from: url)
-                let decoder = JSONDecoder()
-                let response = try decoder.decode(TreeResponse.self, from: data)
-                let items = response.tree.filter { $0.type == "tree" }.sorted { $0.path < $1.path }
-                await MainActor.run {
-                    self.certItems = items
-                    self.isLoadingCerts = false
-                }
-            } catch {
-                await MainActor.run {
-                    self.statusMessage = "Failed to fetch certificates: \(error.localizedDescription)"
-                    self.isLoadingCerts = false
+private func fetchTrees() {
+    Task {
+        let rootURL = URL(string: "https://api.github.com/repos/ProStore-iOS/certificates/git/trees/main")!
+        do {
+            let (data, _) = try await URLSession.shared.data(from: rootURL)
+            let decoder = JSONDecoder()
+            let response = try decoder.decode(TreeResponse.self, from: data)
+
+            let folders = response.tree.filter { $0.type == "tree" }
+
+            var validCerts: [TreeItem] = []
+
+            for folder in folders {
+                guard let folderURL = URL(string: folder.url) else { continue }
+                let (subData, _) = try await URLSession.shared.data(from: folderURL)
+                let subTree = try decoder.decode(TreeResponse.self, from: subData).tree
+
+                let hasP12 = subTree.contains { $0.path.hasSuffix(".p12") }
+                let hasProv = subTree.contains { $0.path.hasSuffix(".mobileprovision") }
+                let hasPassword = subTree.contains { $0.path == "password.txt" }
+
+                if hasP12 && hasProv && hasPassword {
+                    validCerts.append(folder)
                 }
             }
+
+            await MainActor.run {
+                self.certItems = validCerts.sorted { $0.path < $1.path }
+                self.isLoadingCerts = false
+            }
+        } catch {
+            await MainActor.run {
+                self.statusMessage = "Failed to fetch certificates: \(error.localizedDescription)"
+                self.isLoadingCerts = false
+            }
         }
     }
+}
 
     private func fetchBlobContent(url: URL) async throws -> Data {
         let (data, _) = try await URLSession.shared.data(from: url)
@@ -283,3 +301,4 @@ struct OfficialCertificatesView: View {
     }
 }
 
+