Add shareable-slide SVG renderer for published Versions

[bendichter]

Summary

Adds a self-contained renderer at dandiapi/api/slides/ that produces a 1920×1080 CC-0 SVG "shareable slide" for a published Dandiset Version — title, DOI, contributors, key stats, citation, QR code. Researchers can drop this into talks when sharing or reusing data.

This PR is code only — the module is not yet wired into the publish flow, email templates, storage, or any API surface. Those integration points (Celery task, publish-confirmation email, S3 upload, landing-page button) are deliberately deferred and tracked in #2797.

What's in

• dandiapi/api/slides/render.py — render_shareable_slide_svg(version: Version) -> str
• dandiapi/api/slides/dandi_logo.svg — verbatim copy of web/src/assets/logo.svg (fills inlined at module load so the logo nests cleanly inside the slide SVG)
• pyproject.toml / uv.lock — adds qrcode==8.2 (used by the renderer for the SVG QR code; no PIL needed)

What's deliberately out

• No changes to the publish service, Celery tasks, models, mail templates, views, or settings
• No PNG rasterization (the caller can pipe the SVG through librsvg / rsvg-convert later; that decision and the deployment story belong with the integration PR)
• No tests yet — happy to add a basic snapshot test in this PR if reviewers want

Visual preview

A rendered PNG of this code against live metadata for Dandiset 000409 (IBL — Brain Wide Map) will be attached as a comment so reviewers can see it inline.

Test plan

• Reviewers eyeball the rendered output (PNG attached in a comment)
• CI passes (ruff, format)
• Confirm `qrcode==8.2` is acceptable as a runtime dep

Local visual check

# from a Django shell with a published Version v in the DB
from dandiapi.api.slides import render_shareable_slide_svg
from pathlib import Path
Path('/tmp/slide.svg').write_text(render_shareable_slide_svg(v))
# rsvg-convert -w 1920 -h 1080 -o /tmp/slide.png /tmp/slide.svg

Refs #2797

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