[DOCS] Add blog post: Box3D and the 3D world in 1.9.1

[jiayuasu]

Did you read the Contributor Guide?

• Yes, I have read the Contributor Rules and Contributor Development Guide

Is this PR related to a ticket?

• No: this is a documentation update. The PR name follows the format [DOCS] my subject

What changes were proposed in this PR?

Add a blog post, "One More Dimension: Apache Sedona Enters the 3D World", covering the Box3D type and 3D query support that shipped in 1.9.1.

• The type: ST_Box3D and ST_3DMakeBox constructors, ST_XMin through ST_ZMax accessors, BOX3D text form, and a two-box example where the z axis changes the ST_Intersects answer.
• The core demo: Overture Maps buildings for San Diego read from anonymous S3 GeoParquet with bounding-box row-group pruning, turned into per-building Box3D volumes; FAA UAS Facility Map cells turned into above-ceiling airspace boxes; one ST_Intersects box join that finds buildings taller than the drone ceiling above them (31,425 total, 139 in cells where flight is allowed), shown to compile to the planner's RangeJoin on box3d; a hypothetical delivery corridor built from ST_3DMakeBox segments with five obstructions.
• Breadth: aircraft separation with the Geography type plus an altitude band, a below-ground excavation example with negative z, and an ST_3DExtent aggregate.
• A SedonaPyDeck section with the create_geometry_map call used for the 3D building view, plus a paragraph on Box2D, the Python Box3DType bindings, and Flink support.

Includes five images: four generated by the author (an isometric cover and ceiling-plane scene drawn from the real building data, a concept diagram, and a corridor side profile) and one SedonaPyDeck screenshot.

How was this patch tested?

• Every snippet ran against the released artifacts: pip install apache-sedona==1.9.1 with sedona-spark-shaded-3.5_2.12:1.9.1, geotools-wrapper:1.9.1-33.5, and hadoop-aws:3.3.4 from Maven Central, reading s3a://overturemaps-us-west-2 anonymously.
• All numbers in the post (208,477 buildings, 178,384 with height, 585 FAA cells, 233 at 0 ft, 31,425 and 139 join results, 5 corridor obstructions, the BOX3D extent values) are the measured output of those runs, and the console blocks are pasted from them.
• The RangeJoin line is taken from the actual physical plan of the join.
• pre-commit passes, including the manual-stage oxipng hook on all PNGs (idempotent on the second run).
• Verified the rendered page with mkdocs serve: images resolve, code highlighting works, the blog star-CTA hook is appended.

Did this PR include necessary documentation updates?

• Yes, I have updated the documentation.