Use Cloudflare trace by default and validate IPs

Default IPv4 provider is now CloudflareTrace.
Primary uses api.cloudflare.com; fallbacks are literal IPs.
Build per-family HTTP clients by binding to 0.0.0.0/[::] so the trace
endpoint observes the requested address family. Add validate_detected_ip
to reject wrong-family or non-global addresses (loopback, link-local,
private, documentation ranges, etc). Update tests and legacy updater
URLs.
Default to Cloudflare trace and validate IPs

Use api.cloudflare.com as the primary trace endpoint (fallbacks
remain literal IPs) to avoid WARP/Zero Trust interception. Build
IP-family-specific HTTP clients by binding to the unspecified
address so the trace endpoint sees the correct family. Add
validate_detected_ip to reject non-global or wrong-family addresses
and expand tests. Bump crate version and tempfile dev-dependency.

Cargo.lock

@@ -103,7 +103,7 @@ dependencies = [
 
 [[package]]
 name = "cloudflare-ddns"
-version = "2.0.0"
+version = "2.0.1"
 dependencies = [
  "chrono",
  "idna",
@@ -1135,9 +1135,9 @@ dependencies = [
 
 [[package]]
 name = "tempfile"
-version = "3.26.0"
+version = "3.27.0"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "82a72c767771b47409d2345987fda8628641887d5466101319899796367354a0"
+checksum = "32497e9a4c7b38532efcdebeef879707aa9f794296a4f0244f6f69e9bc8574bd"
 dependencies = [
  "fastrand",
  "getrandom 0.3.4",