fix: missing 00000 immutable files with Cardano DB v2

[jpraynaud]

Content

This PR includes a fix on Cardano DB v2 which can not restore a valid full Cardano database:

• embed the 00000 immutable files in the snapshot archive files
• download the 00000 immutable files in the client

Pre-submit checklist

• Branch
  • Tests are provided (if possible)
  • Crates versions are updated (if relevant)
  • Commit sequence broadly makes sense
  • Key commits have useful messages
• PR
  • All check jobs of the CI have succeeded
  • Self-reviewed the diff
  • Useful pull request description
  • Reviewer requested
• Documentation
  • No new TODOs introduced

Issue(s)

Closes #2519

[Copilot]

Pull Request Overview

This PR ensures the 00000 immutable file is included when embedding and downloading Cardano DB snapshots by updating start indices and related tests.

• Start immutable file ranges from 0 instead of 1 in client and aggregator code
• Adjust loops, tests, and expectations to include file number 00000
• Bump mithril-client and mithril-aggregator crate versions

Reviewed Changes

Copilot reviewed 6 out of 6 changed files in this pull request and generated 3 comments.

Show a summary per file

File	Description
mithril-client/src/cardano_database_client/immutable_file_range.rs	Change FIRST_IMMUTABLE_FILE_NUMBER from 1 to 0
mithril-client/Cargo.toml	Bump version to 0.12.8
mithril-aggregator/src/artifact_builder/cardano_database_artifacts/immutable.rs	Introduce FIRST_IMMUTABLE_FILE_NUMBER=0, update loops and tests
mithril-aggregator/src/artifact_builder/cardano_database.rs	Adjust loaded immutable file count (+1)
mithril-aggregator/Cargo.toml	Bump version to 0.7.54

[github-actions]

Test Results

    3 files  ±0     77 suites  ±0   14m 56s ⏱️ -13s
1 929 tests ±0  1 929 ✅ ±0  0 💤 ±0  0 ❌ ±0 
3 272 runs  ±0  3 272 ✅ ±0  0 💤 ±0  0 ❌ ±0 

Results for commit 9a5e305. ± Comparison against base commit 8ff8117.

♻️ This comment has been updated with latest results.

[Alenar]

LGTM

I think you can simplify the tests by shifting the previous upper bound immutable to keep the same number of checks.