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.

.gitignore

@@ -1,63 +1,10 @@
 # Private API keys for updating IPv4 & IPv6 addresses on Cloudflare
 config.json
 
-# Byte-compiled / optimized / DLL files
-__pycache__/
-*.py[cod]
-*$py.class
-
-# C extensions
-*.so
-
-# Distribution / packaging
-.Python
-build/
-develop-eggs/
-dist/
-downloads/
-eggs/
-.eggs/
-lib/
-lib64/
-parts/
-sdist/
-var/
-wheels/
-pip-wheel-metadata/
-share/python-wheels/
-*.egg-info/
-.installed.cfg
-*.egg
-MANIFEST
-
-# PyInstaller
-#  Usually these files are written by a python script from a template
-#  before PyInstaller builds the exe, so as to inject date/other infos into it.
-*.manifest
-*.spec
-
-# Installer logs
-pip-log.txt
-pip-delete-this-directory.txt
-
-# Jupyter Notebook
-.ipynb_checkpoints
-
-# IPython
-profile_default/
-ipython_config.py
-
-# pyenv
-.python-version
-
-# Environments
-.env
-.venv
-env/
-venv/
-ENV/
-env.bak/
-venv.bak/
+# Rust build artifacts
+/target/
+debug/
+*.pdb
 
 # Git History
 **/.history/*