docs: add hash examples notebook

[Brumbelow]

Description of change

Picks up #4154 by @baraiz, which has gone quiet for a few weeks. The notebook itself was already approved — the docs build failed only because it was committed without saved cell outputs, so nbsphinx tried to execute it in CI (no python3 kernel there), exactly as @petyaslavova diagnosed on that PR.

This keeps the original two commits and adds one on top that runs the notebook against a local Redis and saves the outputs, matching the other notebooks in docs/examples/.

Relates to #1744

Pull Request check-list

• Do tests and lints pass with this change?
• Do the CI tests pass with this change (enable it first in your forked repo and wait for the github action build to finish)?
• Is the new or changed code fully tested?
• Is a documentation update included (if this change modifies existing APIs, or introduces new ones)?
• Is there an example added to the examples folder (if applicable)?

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Note

Low Risk
Documentation-only change with no runtime or API impact.

Overview
Adds a Redis Hash examples notebook to the docs and wires it into the examples toctree via docs/examples.rst.

The notebook walks through common hash commands with redis-py (hset/hget, mapping, hexists, hkeys/hvals/hlen, hincrby, hdel, cleanup) using a user:1 profile-style key. Cell outputs are committed so nbsphinx can render the page in CI without executing against a live Redis, consistent with the other notebooks under docs/examples/.

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