Handle non-navigation Android activities safely

[OskarEichler]

Problem

Both Android bridge implementations force-cast React Native's current Activity to NavigationActivity. If an OAuth, relay, permission, or other valid foreground Activity is current—or no Activity is current—the TurboModule or legacy lifecycle/command path can throw ClassCastException instead of waiting for navigation to become foreground again. This also covers the unsafe cast reported in #8048.

Fix

• safe-cast the current Activity in both Turbo and legacy modules
• skip commands while the foreground Activity is not a NavigationActivity, matching existing null-activity gating
• guard legacy host pause/resume and invalidation through the same validated Activity
• reuse the validated legacy Activity/Navigator within lifecycle callbacks
• remove an unreachable second null check inside Turbo setRoot
• replace touched deprecated currentActivity property access with getCurrentActivity()

Breaking changes

None. A state that previously crashed is now logged accurately and safely skipped; normal NavigationActivity command/lifecycle behavior is unchanged. Commands are not queued by this patch.

Test plan

• Added a Turbo regression invoking a command with an AppCompatActivity foreground; exact baseline throws ClassCastException.
• Added legacy coverage for command handling, host resume/pause, and invalidation with the same foreign Activity.
• Focused regressions pass 4/4.
• Full Android RNN unit suite passes: 699 successes, 0 failures, 2 skipped.
• git diff --check passes.