Drop the typescript7 alias once openapi-ts supports the TypeScript 7 API

[FelixTJDietrich]

We type-check on TypeScript 7 through a typescript7 npm alias, while typescript itself stays pinned to 6.0.3. That split exists for exactly one reason.

@hey-api/openapi-ts calls the TypeScript compiler API, which 7.0 does not ship:

@hey-api/openapi-ts/dist/init-Bi6_Uyy_.mjs:4153
	newLine: ts.NewLineKind.LineFeed,
TypeError: Cannot read properties of undefined (reading 'LineFeed')

Everything else we assumed was blocking turned out not to be. Storybook and react-docgen-typescript build fine against 7.0.2 and produce identical output (515 docgen entries either way).

TypeScript 7.1 is expected to ship a new programmatic API. Once @hey-api/openapi-ts supports it, drop the alias and pin typescript to 7.

Done when

• webapp/package.json and the root package.json have a single typescript dependency on 7.x
• typecheck, build and typecheck:scripts call plain tsc again
• the //typecheck note explaining the alias is removed
• pnpm run generate:api still produces an unchanged webapp/src/api

[FelixTJDietrich]

Still blocked. Checked @hey-api/openapi-ts@0.99.0 (we are on 0.97.1): its dist/ still contains NewLineKind and 268 createPrinter/ts.factory call sites, so it continues to depend on the TypeScript compiler API that 7.0 removed. The peer range is unchanged at >=5.5.3 || >=6.0.0 || 6.0.1-rc — still accepting 7 without warning. No action; re-check on the next minor.