Migrate cloudflare-ddns to Rust

Add Cargo.toml, Cargo.lock and a full src/ tree with modules and tests
Update Dockerfile to build a Rust release binary and simplify CI/publish
Remove legacy Python script, requirements.txt, and startup helper
Switch .gitignore to Rust artifacts; update Dependabot and workflows to
cargo
Add .env example, docker-compose env, and update README and VSCode
settings

Remove the old Python implementation and requirements; add a Rust
implementation with Cargo.toml/Cargo.lock and full src/ modules, tests,
and notifier/heartbeat support. Update Dockerfile, build/publish
scripts, dependabot and workflows, README, and provide env-based
docker-compose and .env examples.

Cargo.toml

@@ -0,0 +1,21 @@
+[package]
+name = "cloudflare-ddns"
+version = "2.0.0"
+edition = "2021"
+description = "Access your home network remotely via a custom domain name without a static IP"
+license = "GPL-3.0"
+
+[dependencies]
+reqwest = { version = "0.12", features = ["json", "rustls-tls"], default-features = false }
+serde = { version = "1", features = ["derive"] }
+serde_json = "1"
+tokio = { version = "1", features = ["full"] }
+regex = "1"
+chrono = { version = "0.4", features = ["clock"] }
+url = "2"
+idna = "1"
+if-addrs = "0.13"
+
+[dev-dependencies]
+tempfile = "3.26.0"
+wiremock = "0.6"