Add refresh and pagination to Android catalog

[markmur]

What changes are you making?

• Add native pull-to-refresh to the Android sample catalog.
• Increase the initial and subsequent catalog page size to 50 products.
• Fetch and append additional catalog pages until the Storefront API reports there are no more pages.
• Bypass Apollo's in-memory cache for manual refreshes while preserving cache-first loading otherwise.
• Keep paging state in the view model so refreshes create a fresh paging source.

[github-actions]

Package Size

Platform	Artifact	Base	Head	Delta
Android	release AAR	364.8 KiB	364.8 KiB	0 B

Android file breakdown

File	Base	Head	Delta
classes.jar	388.4 KiB	388.4 KiB	0 B
res/layout/checkout_view_content.xml	2.6 KiB	2.6 KiB	0 B
res/layout/checkout_sheet_content.xml	2.0 KiB	2.0 KiB	0 B
res/values/values.xml	1.3 KiB	1.3 KiB	0 B
R.txt	1.2 KiB	1.2 KiB	0 B
AndroidManifest.xml	922 B	922 B	0 B
proguard.txt	798 B	798 B	0 B
res/drawable/close.xml	431 B	431 B	0 B
res/menu/checkout_menu.xml	354 B	354 B	0 B
META-INF/com/android/build/gradle/aar-metadata.properties	157 B	157 B	0 B

Measured from the PR base SHA and PR head SHA. The file breakdown shows uncompressed sizes within each package artifact, so individual files do not sum to the compressed artifact total. This comment reports package artifact sizes only; it is not a final app binary-size report.