Add DataTalks.Club social banners and Luma event artwork

Scope

Integrate the supplied DataTalks.Club social banner direction into the shared banner generator and the public website.

• Add the DataTalks.Club template and reusable data slots to banner-generator.
• Support event, podcast, workshop, article, book, and course artwork variants.
• Support the explicit 1000x1000 Luma event output, plus OG and YouTube exports.
• Generate representative event artwork for the public event catalogue.
• Render the square artwork in event detail pages following the Luma-like event-header convention.
• Preserve registration, recording, accessibility, and existing event routes.

Boundaries

• Do not add a runtime Luma dependency.
• Do not migrate registration/provider data.
• Do not redesign the shared site shell.
• Keep all generated public artwork free of attendee or private registration data.

Acceptance criteria

• Generator tests cover template resolution, escaping, examples, and the 1000x1000 size contract.
• Generated event assets are valid 1000x1000 PNGs and are stored in the website static asset pipeline.
• Mapped event detail pages visibly render artwork with accessible alt text.
• Event detail pages publish OG/Twitter image metadata and Schema.org Event image data.
• Unmapped events retain the existing no-image fallback.
• Desktop and mobile browser checks show no layout overflow and the asset loads successfully.

Verification

• Banner generator: 22 tests, ruff check, and all eight DTC examples rendered.
• Website: 43 focused Django event tests, 8 template-source tests, ruff check, and browser checks at 1440px and 390px.
• Full content suite remains data-fixture blocked on this production-prep checkout; its unrelated media/projection failures are recorded in the handoff.

The issue names the banner-generator, website static asset pipeline, event detail pages, Django event tests, and template-source tests. Start by reviewing those verification targets and the checked acceptance criteria; the stated definition of done is valid 1000x1000 PNGs, accessible event artwork, metadata, fallback behavior, and passing browser checks.