docs: describe the current floci storage wiring in local-development (FB-2197) (#35)

**Background**

FB-2197: filed for the helm-test CI breakage after the `20260713060957`
appVersion bump; the functional fix landed concurrently via #34
(FB-2191), which this PR originally duplicated. Slimmed down to the
remaining delta.

**Summary**

`docs-internal/local-development.md` still described the removed storage
schema (`type: minio` with hardcoded credentials). Updated to match the
current wiring: `managed_table_storage: s3` + `aws.endpoint` at floci,
dummy AWS credentials via `engineSpec.extraEnv`.

**Test Plan**

Docs-only; no behavior to test.

<!-- CURSOR_SUMMARY -->
---

> [!NOTE]
> **Low Risk**
> Documentation-only change with no runtime or configuration impact.
> 
> **Overview**
> **Why floci** in `docs-internal/local-development.md` now states that
**floci is zero-auth**: signed requests are accepted without configuring
dummy AWS credentials, complementing the existing explanation of
`managed_table_storage: s3` and `aws.endpoint` in `values-dev.yaml`.
> 
> <sup>Reviewed by [Cursor Bugbot](https://cursor.com/bugbot) for commit
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Co-authored-by: Florian Strübe <florian@firebolt.io>

Author: gm42

docs-internal/local-development.md

@@ -24,8 +24,7 @@ make test
 | `make dev` | `make upgrade-dev` |
 
 ## Why floci
-
-The metadata images shipped after 2026-05-13 refuse local-filesystem managed storage in dedicated-Pensieve mode. `values-dev.yaml` points `customEngineConfig.storage` at floci (`managed_table_storage: s3` plus `aws.endpoint`) so local installs use object storage without cloud infrastructure.
+The metadata images shipped after 2026-05-13 refuse local-filesystem managed storage in dedicated-Pensieve mode. `values-dev.yaml` points `customEngineConfig.storage` at floci (`managed_table_storage: s3` plus `aws.endpoint`) so local installs use object storage without cloud infrastructure. floci is zero-auth, so any signed request passes without the need to set up (dummy) AWS credentials.
 
 ## Reset floci