Add passive Buy Me a Coffee support links

[omar-hanafy]

What changed

• add GitHub's native Buy Me a Coffee funding configuration
• add plain Support links to the desktop and mobile site navigation and shared footer
• add one quiet support note to the standalone plugin guide
• add contract and browser coverage for the exact URL, responsive discoverability, and the absence of embedded BMC scripts, widgets, or images

Why

People who want to support GlyphPact should find the path quickly, while everyone else should be able to use the compiler and site without donation prompts, popups, or visual noise.

Release boundary

This intentionally leaves normal CLI output, generated artifacts, JSON, the root package long description, and PyPI 1.0.1 metadata unchanged. A fresh 1.0.1 build remains byte-identical to the attested plugin wheel.

Validation

• 544 Python tests passed, 2 platform-gated tests skipped
• Ruff format and lint passed
• mypy passed for 22 source files
• 37 focused release-contract tests passed
• Astro type-check, brand, production build, claim, link, metadata, and sitemap checks passed
• 36 Playwright responsive, accessibility, layout, and support-placement tests passed
• 15 plugin tests plus 12 subtests passed
• plugin validation passed
• Twine checks passed for wheel and sdist
• fresh and bundled wheel SHA-256 matched: ae42d5bb639b69027c41adf23ccf394a0dffd1e55ccbfe4c18fe66f39c3bbda3