Remove CEF: the web content crate, ElyMark's page, their packaging, licences and tests (C14.5)

PRD and agents.md name the native route; ElyMail's body will not use
CEF or Electron. ElyMark's package carries the KaTeX fonts' OFL.

Co-Authored-By: Claude Opus 5.5 (1M context) <noreply@anthropic.com>

Cargo.toml

@@ -49,7 +49,6 @@ objc2-core-media = { version = "0.3", default-features = false, features = ["std
 objc2-core-video = { version = "0.3", default-features = false, features = ["std", "CVBuffer", "CVImageBuffer", "CVPixelBuffer"] }
 objc2-core-foundation = { version = "0.3", default-features = false, features = ["std", "CFString", "CFCGTypes"] }
 core-video = "0.5"
-cef = { git = "https://github.com/tauri-apps/cef-rs", rev = "a712ad9bacd234c050631a95b9745b27d346b7cc", default-features = false }
 core-foundation = "0.10"
 objc2 = "0.6"
 security-framework = "3.7"
@@ -61,7 +60,6 @@ ely-lok = { path = "crates/ely-lok" }
 ely-office = { path = "crates/ely-office" }
 ely-pdf-engine = { path = "crates/ely-pdf-engine" }
 ely-platform = { path = "crates/ely-platform" }
-ely-web-content = { path = "crates/ely-web-content" }
 ely-ui = { path = "crates/ely-ui" }
 
 [workspace.lints.clippy]