chore(release): bump versionName to 1.3.0-rc.4

[psjostrom]

## What's new since rc.3

### Story screen fixes
- The "Your April Story is ready" snackbar no longer re-fires after restart when you've already viewed April but tapped ← to browse March or earlier. The viewed-month marker now monotonically advances and is enforced atomically in the storage layer (no future caller can downgrade it accidentally).
- The ← / → arrows on the Story screen now visibly grey out at the data boundaries, instead of looking enabled while clicks were silently no-ops.
- The back button uses the same control-color pattern for consistency.

Test plan

• Open Stats > Story → April → tap ← back to March → close → reboot device. No false "Your April Story is ready" snackbar on next launch.
• Open Stats > Story at last completed month → → arrow visibly faded.
• Tap ← repeatedly to your earliest reading's month → ← arrow visibly faded.
• Tap a faded arrow at a boundary — nothing happens (no flicker, no navigation).
• Mid-range month → both arrows visibly enabled, navigation works.
• Verify retention setting + dialog still work end-to-end (regression check on the rc.3 features).

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