feat(db): compress Receipts rows with zstd

[kariy]

Summary

• Store new Receipts rows as an explicit envelope plus zstd(postcard(receipt)) while keeping reads compatible with legacy raw-postcard rows.
• Treat malformed enveloped rows as corruption instead of silently falling back to the legacy decoder.
• Add focused codec and Receipts table round-trip tests, and document the mixed-format receipt storage in docs/database.md.

Compatibility

• No db.version bump in this phase.
• New Katana code can read existing databases that still contain legacy raw-postcard receipt rows.
• Older Katana binaries are not guaranteed to read databases after compressed receipt rows have been written.

[codecov]

Codecov Report

❌ Patch coverage is 99.29078% with 1 line in your changes missing coverage. Please review.
✅ Project coverage is 68.71%. Comparing base (9bde0ae) to head (b76ca30).
⚠️ Report is 300 commits behind head on main.

Files with missing lines	Patch %	Lines
crates/storage/db/src/models/receipt.rs	99.05%	1 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main     #465      +/-   ##
==========================================
- Coverage   73.32%   68.71%   -4.62%     
==========================================
  Files         209      280      +71     
  Lines       23132    34143   +11011     
==========================================
+ Hits        16961    23460    +6499     
- Misses       6171    10683    +4512     

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[kariy]

Preliminary test done on a database filled with mainnet data of about ~3M blocks, we're able to reduce the Receipts table size by about ~30%.