Attest native source identity from certified PostgreSQL state

[Ivanbeethoven]

Attest native source identity from a persisted UUID and an actual certified native publication. One repeatable-read primary PostgreSQL snapshot verifies the READY association, bounded commit/tree bytes, typed Git hashes, parsers and commit-to-root-tree relationship before constructing the opaque SourceSnapshot and NamespaceView. Explicit bootstrap serializes with native writers and preserves uncertain-commit retries; migration creates no implicit identity.

The object byte checks use the stored payload. The Tree converter stores size metadata as zero, so that field is not an object-length authority. Regression tests prove a valid baseline, show unrelated size metadata cannot change the attested identity, and retain rejection of corrupt, oversized, malformed, missing and mismatched objects.

Complete Linux repository gates passed at a1f02ce4288ade52d58aee4e133df7fcbc92631a: https://github.com/gitmono-dev/mega2/actions/runs/37343889787.

• Formatting, strict all-target/all-feature Clippy, build, test build, isolated PostgreSQL/Redis/RustFS dependencies, source .env.test && cargo test --all, and cleanup passed.
• All 18 test targets passed: 2,333 tests passed, 0 failed, and 2 pre-existing tests remained ignored. The library passed 2,106 tests.
• The log contains successful results for all 76 selected identity, preparation-expiry, metadata-install, lease, namespace, filter and migration regressions, including all 13 native source identity tests.
• Two independent source reviews passed. The branch and PR match the tested commit, and no unresolved review threads remain.

This private factory grants no read, policy or retention authority. HTTP/runtime serving, physical GC, MST/2 wire and schema2 remain outside this change. The PR is stacked on #47 and pins the reviewed namespace codec revision. No deployment or benchmark result is claimed.