Fix release links in README: use absolute Gitea URLs, drop 'GitHub' wording

The relative '../../releases/latest' links did not resolve on Gitea. Point the
fabrication-data links at the absolute releases/latest URL and rename the
fabrication zip reference to esp-sensair-v1.0.0-gerbers.zip.

.gitignore

@@ -16,7 +16,7 @@ netlist/
 reports/
 
 # Fabrication outputs (Gerbers, drills, job file, upload zip) are derived
-# artifacts published as GitHub Release assets, not committed to the tree.
+# artifacts published as release assets, not committed to the tree.
 # Regenerate from KiCad and attach the zip to the matching release tag.
 gerber/
 *.gbr.bak