task: redraw or retire the orphaned funding-ladder diagram (img/building/ecosystem-grants.png)

Follow-up from #2301.

## What is true today

`img/building/ecosystem-grants.png` is referenced by **no page**:

```
$ git grep -n "ecosystem-grants" -- '*.mdx' '*.jsx' '*.json'
(no matches)
```

It was embedded on `/build-on-celo/fund-your-project` and removed in #2301 because the diagram plots **Proof of Ship** as the entry rung of the funding ladder, and that program is sunset. It is a raster file, so the label could not be edited in that PR.

## Why it needs a redraw rather than a re-link

The diagram had already drifted from the page independently of Proof of Ship. It shows four programs:

| In the diagram | On the page today |
|---|---|
| Proof of Ship | sunset, removed |
| Prezenti Boost Grant | page links Prezenti generally, no tiers |
| Prezenti Anchor Round | not mentioned |
| Celo Builder Fund | **not mentioned anywhere in the repo** |

It also carries specific thresholds (MAU 10/100/1000, daily txs 10/100/500, TVL 1k/10k/50k, support bands $0–5k through $25–100k) that appear in no text. Per AGENTS.md §6, images must not carry information that is not also in the text — agents and screen readers do not see them. So this is not a case of swapping one label.

## The page it left behind

`/build-on-celo/fund-your-project` is now thin: two programs (Prezenti, Verda Ventures) and a newsletter link. If the funding ladder still has rungs, the page needs them in text first; the diagram should then illustrate what the text says.

## Acceptance criteria

- [ ] Decide whether a funding-ladder diagram is still wanted
- [ ] If yes: redraw without Proof of Ship, reconcile "Celo Builder Fund" against reality, and put every threshold in the page text as well
- [ ] If no: `git rm img/building/ecosystem-grants.png`
- [ ] Either way `/build-on-celo/fund-your-project` reflects the programs that actually run

Read AGENTS.md §6 and inspect /build-on-celo/fund-your-project alongside img/building/ecosystem-grants.png. Run the documented git grep to confirm current references, then establish which funding programs and thresholds are supported by page text. Done means the diagram is either retired or redrawn consistently with the page, and the page reflects programs that actually run.

Written by the indexing model from the issue text.