fix(mobile): guard against null certificate entries causing crash

[jorbuedo]

Summary

• Fixes unhandled cannot read property 'kind' of null crash when viewing transaction history
• After failed storage migrations (introduced in 7.0.3 hardening), the transaction cache can contain corrupted certificate arrays with null entries
• Adds null guards at 4 consumer sites (transactionSummary.ts, operationDisplay.ts, getOperationTypeKey.ts, useFormattedTxFromWalletTransaction.tsx)
• Also filters null certificates at the storage deserialization layer in transactionManager.ts to prevent the issue at the source

Test plan

• Open app with a wallet that has staking/governance transactions in history
• Verify transaction list renders without crash
• Verify transaction details screen renders certificates correctly
• Simulate corrupted storage by manually inserting a null entry in a transaction's certificates array in MMKV, verify no crash

🤖 Generated with Claude Code

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Note

Low Risk
Defensive filtering/guards around corrupted cached transaction data; behavior change is limited to ignoring null certificate entries and bumping app/package versions.

Overview
Prevents crashes when rendering transaction history/details by filtering out null entries in transaction certificates both at persistence boundaries (parseTx in transactionManager.ts) and at key UI/logic consumers (formatted tx hook, operation display/type key, and MIR reward summary).

Also bumps the mobile app/package version from 7.0.3 to 7.0.4 (including lockfiles) for the release.

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[codecov]

Codecov Report

❌ Patch coverage is 20.00000% with 8 lines in your changes missing coverage. Please review.
✅ Project coverage is 21.98%. Comparing base (e9e7e9e) to head (1fe41c3).
⚠️ Report is 1 commits behind head on develop.

Additional details and impacted files

@@           Coverage Diff            @@
##           develop    #4473   +/-   ##
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  Coverage    21.97%   21.98%           
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  Files         1412     1412           
  Lines        36183    36189    +6     
  Branches      8169     8170    +1     
========================================
+ Hits          7953     7955    +2     
- Misses       27626    27630    +4     
  Partials       604      604           

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