fix: remove 6 stale or deprecated dependencies

[Becheler]

Reducing boost dependencies with C++ modernization. It's pure hygiene, not user-facing, breaks no API.

Before submitting

• This PR targets the develop branch.
• I searched for an existing PR or issue covering the same change.
• My contribution is licensed under the Boost Software License 1.0.

Type of change

• Bug fix
• New feature or API addition
• Refactor (no behavior change)
• Documentation
• Build, CI, or tooling
• Other (specify below)

Does this PR introduce a breaking change?

• Yes (describe migration impact below)
• No

What this PR does

A few commits of hygiene:

1. Remove Boost.Conversion. It was used only in DFS for implicit_cast, when copy-initialization (Vertex u = expr;) requires an implicit conversion exercising the exact same constraint boost::implicit_cast enforces.
2. Remove stale boost.bind dependency (not use anywhere)
3. Remove stale boost.typeof dependency (included but not used)
4. Remove boost.move dependency
5. Remove boost.foreach dependency
6. Remove boost.numeric_conversion dependency

Motivation

Users complained they need to drag the entire Boost ecosystem to use Boost.Graph. Meanwhile, many dependencies were pulled in older C++ versions for utilities that C++14 now provides.

Testing

Checklist

• Existing tests pass (b2 in the test/ directory).
• New behavior is covered by a test, or this is a docs / build / refactor change.
• Documentation was updated if user-facing behavior changed.
• No new compiler warnings on the platforms I built against.

[github-actions]

Boost dependency footprint vs develop (auto-generated).
PR run 29431837644 vs develop run 29397385834 (369326a022).

Header-inclusion weights (graph files pulling each direct dependency in):

Dependency	develop	PR	Δ
foreach	3	0	-3
conversion	1	0	-1
move	1	0	-1
numeric~conversion	1	0	-1
typeof	1	0	-1

Transitive Boost modules: 70 → 69 (-1)

• removed: foreach

[github-actions]

Compiler-warning counts vs develop (auto-generated).
PR run 29431838713 vs develop run 29397386211 (369326a022).

Job	Baseline	After	Delta
macos (clang, 14)	4	4	0
macos (clang, 17)	4	4	0
macos (clang, 20)	4	4	0
ubuntu (clang-19, 14)	4	4	0
ubuntu (clang-19, 17)	4	4	0
ubuntu (clang-19, 20)	4	4	0
ubuntu (clang-19, 23)	4	4	0
ubuntu (gcc-14, 14)	10	10	0
ubuntu (gcc-14, 17)	10	10	0
ubuntu (gcc-14, 20)	10	10	0
ubuntu (gcc-14, 23)	10	10	0
windows_msvc_14_3 (msvc-14.3)	971	971	0

[jeremy-murphy]

Awesome. Just need to remove the dependences from the CMake configuration too.