Update meetup content for September 2026 Practi"FALL" Prints challenge

- Archive August 2026 Gridfinity Extravaganza
- Set September 2026 Practi"FALL" Prints as active challenge
- Set October 2026 as upcoming challenge
- Create announcements/September2026.md and challenges/September-2026/
- Update Important-Dates, Readme, challenges.md, and sync wiki-content-gitea
- Update wiki-fargo3d submodule pointer

Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>

challenges/September-2026/readme.md

@@ -0,0 +1,39 @@
+---
+gitea: none
+tags:
+ - challenge
+ - challenge-010
+---
+[← Back to Home Page](Home)
+
+# Current Challenge: September 2026
+
+## Challenge: Practi"FALL" Prints
+
+As we head into fall, it is time to show off the practical power of 3D printing with **Practi"FALL" Prints**! 
+
+Whether it is an everyday household fix or a clever workshop tool, bring in a practical print that solves a problem or makes life easier.
+
+### The Focus: Functional Utility & Everyday Practicality
+The goal is to design or print a functional item that serves a practical purpose. This can be anything from a simple door stop, cord clip, or drawer organizer, to a crazy multi-levered bottle or can opener, tool jig, or replacement bracket!
+
+### Submission Requirements
+
+* **Physical Model**: Bring your practical print to the **September 16th, 2026** meetup.
+* **Range of Entries**: Anything functional qualifies—from simple everyday utility items to complex mechanical openers or tools.
+* **The Story**: Be ready to demonstrate or explain what problem your print solves, how you use it, and your printing/design approach (materials, infill, orientation for strength, etc.).
+
+### Judging & Prize
+
+* **Voting**: The group will vote on their favorite entry based on practical usefulness, creativity, and execution.
+* **Prize**: The winner will receive a **free spool of filament**!
+
+### Timeline
+
+* **Challenge Announcement**: August 19th, 2026 (at August meetup)
+* **Show & Tell / Voting**: September 16th, 2026 (during September meetup)
+* **Winner Announcement**: September 16th, 2026 (end of September meetup)
+
+---
+
+**This challenge is currently active for September 2026**