Add project fingerprints and semantic diffs

[erseco]

Summary

• add exact archive fingerprints with streaming ZIP-entry hashing
• add normalized logical-content fingerprints
• exclude volatile package identity/version metadata from normalized fingerprints
• include parsed project structure and project resource bytes in content fingerprints
• add hasSameContentAs() for normalized content equality
• add semantic project diffs for:
  • core metadata
  • pages
  • blocks
  • iDevices
  • added/removed/modified resources
• expose archive/content fingerprints in detailed serialization
• keep ZIP packaging differences separate from logical content changes

Stack

This PR is stacked on #23 and targets perf/indexed-parser.

Fingerprint semantics

getArchiveFingerprint() hashes the exact archive bytes.

getContentFingerprint() normalizes logical project data, excludes volatile fields such as odeId, odeVersionId and the eXeLearning application version, and includes hashes of project resource bytes.

Tests

Covers:

• different ZIP/package IDs with identical logical content
• exact archive fingerprint differences
• stable normalized content fingerprints
• binary resource modifications
• semantic metadata changes
• diff output for modified resources

CI is green on PHP 8.0–8.5, coverage, Composer validation, PHPCS and PHPStan.