v1.0.73: auto-upgrade http:// to https:// for WebDAV

Zahra's sync pair was configured with http://dav.khodak.me. Traefik has
a global HTTP->HTTPS redirect, but PROPFIND/PUT/MOVE are not followed
through redirects by OkHttp — so every WebDAV operation was getting
redirected and silently failing. 1072 logins, 0 actual DAV operations.

Silently rewrite http:// to https:// at the provider level so users
never need to reconfigure.

app/src/main/kotlin/com/syncflow/data/providers/webdav/WebDavProvider.kt

@@ -27,7 +27,14 @@ import java.util.concurrent.TimeUnit
 open class WebDavProvider(protected val account: CloudAccount) : CloudProvider {
 
     protected open val baseUrl: String
-        get() = account.serverUrl?.trimEnd('/') ?: ""
+        get() {
+            val raw = account.serverUrl?.trimEnd('/') ?: ""
+            // Silently upgrade http:// → https:// so that phone configs saved with
+            // http:// still work when the server only accepts HTTPS (e.g. behind Traefik
+            // with a global HTTP→HTTPS redirect). WebDAV methods (PROPFIND, MKCOL, MOVE)
+            // are not followed through redirects by OkHttp, so they would silently fail.
+            return if (raw.startsWith("http://")) "https://" + raw.removePrefix("http://") else raw
+        }
 
     protected val client: OkHttpClient by lazy {
         val creds = Json.parseToJsonElement(account.credentialJson).jsonObject