chore(deps): bump Compose BOM to 2026.09.00

Measure-pass defect in compose ui 1.12.0: layoutChildrenBlock clobbered
the isPlacingForAlignment flag of child nodes during alignment
placement, so sheet anchors were recalculated from a stale content size.

compose ui 1.12.1 preserves and restores child placement flags, so the
anchor is computed from a consistent content size on the first frame.

gradle/libs.versions.toml

@@ -2,7 +2,7 @@
 aboutlibraries = "15.2.0"
 activity_compose = "1.13.0"
 agp = "9.3.1"
-compose_bom = "2026.08.00"
+compose_bom = "2026.09.00"
 core = "1.19.0"
 datastore_preferences = "1.2.1"
 documentfile = "1.1.0"