[GH-3033] [DOCS] Fix Whimsy site-check failures: ASF footer links, nav URLs, and external GitHub API call (GH-3033)

[jiayuasu]

What this PR does

Fixes the Whimsy project website checks for Sedona (https://whimsy.apache.org/site/project/sedona), which were failing nearly every required-content check. Three changes:

1. docs-overrides/partials/copyright.html — Adds the ASF-required links to the rendered site footer so they appear on the homepage where Whimsy looks: License, Events, Sponsorship, Thanks, Security, Privacy, and Trademarks. Also makes the copyright notice itself a link (Whimsy's Copyright check expects a link matching (©|Copyright).*apache). Previously these links only existed as nav: entries in mkdocs.yml and never rendered in the footer.

2. mkdocs.yml — Removes the stray " target="_blank that had been appended to the License, Events, Sponsorship, Thanks, Security, and Privacy nav URLs, which produced malformed hrefs.

3. docs-overrides/partials/source.html (new) — Overrides the Material for MkDocs source partial to render the repo link without data-md-component="source", so the theme no longer fetches stars/forks/version from api.github.com. Those calls were being refused by the site CSP and showed up as failed external resources in the Whimsy "Resources" check. The ASF-sanctioned Scarf and Matomo pixels are unaffected.

Did you read the Contributor Guide?

• Yes.

Is this PR related to a ticket?

• Yes, the PR name follows the format [GH-XXX] my subject. Closes Apache Sedona Website Check: Checking ASF Project Websites for required and disallowed content #3033

[Copilot]

Pull request overview

This PR updates the MkDocs configuration and theme overrides for the Sedona project website to satisfy Apache Whimsy required-content checks and to avoid blocked external GitHub API requests during site rendering.

Changes:

• Fix malformed ASF navigation URLs in mkdocs.yml by removing stray target="_blank fragments.
• Update the footer partial to render ASF-required links (License, Events, Sponsorship, Thanks, Security, Privacy, Trademarks) and a Whimsy-detectable copyright link.
• Add a Material for MkDocs source.html partial override to render the repository link without triggering GitHub API metadata fetching.

Reviewed changes

Copilot reviewed 3 out of 3 changed files in this pull request and generated no comments.

File	Description
mkdocs.yml	Cleans up malformed external ASF nav URLs so generated hrefs are valid.
docs-overrides/partials/source.html	Overrides the theme “source” partial to render the repo link without the GitHub API metadata component.
docs-overrides/partials/copyright.html	Adds ASF-required footer links and adjusts copyright rendering for Whimsy checks.

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