Add high-level diagrams + project map to connect concepts (docs)

Feedback:
Docs would benefit from high-level diagrams and a project map that connects **concepts, tooling, and contract logic.** Right now, it can feel fragmented without a “big picture” view.

Ask:
- Add diagrams showing how the main pieces (contracts, tooling, proving, accounts, etc.) fit together.
- Provide a project map that connects concepts to the right crates/SDKs/docs.

Why:
Gives developers a mental model of the whole system and makes it easier to navigate from big-picture to details.

**This feedback came through DevRel applications.**