chore(catalog): record boot-3.4.12

[github-actions]

Adds boot 3.4.12 → boot-3.4.12 and the converted tree under markdown/boot/3.4.12/, published by the release workflow.

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Summary by cubic

Adds Spring Boot 3.4.12 to the catalog by recording boot-3.4.12 in catalog.json and publishing its converted documentation tree under markdown/boot/3.4.12/.

• The catalog now lists 3.4.12 with its release timestamp and tag.
• The new doc set includes 145 converted pages, license, and notice files generated by the release workflow.
• No existing entries or behavior change beyond the new version.

^{Written for commit bde89ca. Summary will update on new commits.}

[greptile-apps]

PR author is in the excluded authors list.

[sonarqubecloud]

Quality Gate passed

Issues
0 New issues
0 Accepted issues

Measures
0 Security Hotspots
0.0% Coverage on New Code
0.0% Duplication on New Code

See analysis details on SonarQube Cloud

[codacy-production]

Up to standards ✅

🟢 Issues 0 issues

Results:
0 new issues

View in Codacy

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TIP This summary will be updated as you push new changes.}

[amondnet]

Superseded by #72, which registers all 45 Spring Boot 3.x releases in one commit — every catalog branch is cut from the default branch, so these 45 pull requests all rewrite the same projects object and cannot merge independently. The release itself is published and unaffected.