Add conandeps: dependency, binary-availability and override report for Conan 1.66

conandeps.py lists direct and indirect dependencies of a conanfile.py,
checks whether Release/Debug/RelWithDebInfo binaries exist on a remote for
the exact profile, and reports explicit (override=True) and implicit
requirement overrides both as a list and on the edges of the dependency
tree. Text output by default, optional self-contained HTML via --html.

The graph is built once per build type through Conan's own info API and
each node's binary status is read back, so package_id modes and options
are honoured like a real install. Overrides are parsed from Conan's WARN
output since 1.x does not record them on the graph.

Development runs inside a pinned podman container (Containerfile, dev.sh)
with Conan 1.66 on Python 3.11. Tests start a throw-away conan_server and
verify missing-binary and override detection end to end.

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01EYNdaGDrpaqDyT8QtrTQbM

.gitignore

@@ -0,0 +1,4 @@
+__pycache__/
+.pytest_cache/
+.ruff_cache/
+*.html