Add explicit return-type annotations to `NotionBlocks` and `JsonLdScript` exported components

[ooloth]

Why

NotionBlocks and JsonLdScript are exported components at public API boundaries with no return-type annotation, so callers cannot understand the contract from the signature alone and must read the function body.

Current state

io/notion/ui/NotionBlocks.tsx line 13 exports function NotionBlocks({ blocks }: Props) with no return type. seo/json-ld/script.tsx line 20 exports function JsonLdScript(props: JsonLdScriptProps) with no return type. Both are at public module boundaries.

Ideal state

• Both functions carry explicit return types (ReactElement or JSX.Element as appropriate).
• A reader can understand each function's contract from the signature without reading the body.
• The return type serves as a compiler-checked contract assertion.

Starting points

• io/notion/ui/NotionBlocks.tsx — line 13
• seo/json-ld/script.tsx — line 20

QA plan

1. Open both files and verify each function signature includes a return type annotation.
2. Change the return type to an incompatible type — expect a compile error.
3. Run tsc --noEmit — expect no type errors.

Done when

Both NotionBlocks and JsonLdScript have explicit return-type annotations and the return types are verified by the TypeScript compiler.