fix(notifications): show total zap count instead of 24h-only sats

[dmnyc]

Summary

• The zap badge in the notifications summary bar was computing its count and sats total from only the last 24 hours, while the notification list itself has no time filter. Any zap older than 24h would appear as a visible row but contribute nothing to the badge, leaving it stuck at 0.
• Additionally, the badge was displaying total sats (from bolt11 decoding) rather than a count. If bolt11 decoding failed for any receipt — for example because the invoice encodes no amount in the HRP — sats stayed 0 and the badge showed 0 even with visible zap rows.

Changes:

• Remove the 24h cutoff from computeSummary24h() so the counts reflect every item in the buffer (matching what the list shows)
• Change the zap badge label from sats to zapCount, consistent with how every other category (reactions, replies, reposts) is displayed

Test plan

• Open Notifications tab — zap badge shows a non-zero count when zap rows are visible
• Zaps older than 24h appear in the list and are included in the count
• Tapping the ⚡ badge still filters the list to zaps only
• Other category counts (reactions, replies, etc.) are unaffected