Release 0.7.0 (#508)

Bump the workspace to 0.7.0 and write the 0.7.0 release notes. Minor bump: the design format moved to 15 (sketches on cylinder caps and sheet metal panels), so 0.6 can't open 0.7 saves, and new features landed (Select Other, per-edge flanges, sketches on caps and sheet metal faces).

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

Cargo.toml

@@ -5,7 +5,7 @@ members = ["crates/*", "apps/*", "xtask"]
 exclude = ["vendor"]
 
 [workspace.package]
-version = "0.6.0"
+version = "0.7.0"
 edition = "2024"
 license = "MIT OR Apache-2.0"
 rust-version = "1.95"