fix(metadata): ensure EPUB version-aware metadata writing

[Shaglock]

Summary

Fixes #2997

EpubMetadataWriter unconditionally wrote EPUB3-only constructs into all EPUB files regardless of version. This produced invalid OPF documents that fail Amazon's Send to Kindle validation (error E999) and epubcheck validation (RSC-005, PKG-007).

Root Cause

When Booklore modifies EPUB metadata, it always wrote EPUB3 constructs (e.g., opf:file-as/opf:role attributes on dc:creator, <meta property="..."> elements, prefix attribute on <package>) regardless of whether the EPUB is version 2.0 or 3.0. For EPUB3 files, using opf: attributes on dc:creator is invalid per the spec — EPUB3 requires <meta refines="#id"> elements instead.

Changes

All changes are in EpubMetadataWriter.java (source) and EpubMetadataWriterTest.java (tests):

• createCreatorElement: EPUB3 now uses <meta refines="#id"> for file-as and role with marc:relators scheme; EPUB2 keeps opf: attributes on dc:creator
• addFolderContentsToZip: mimetype is now STORED (uncompressed) and written as the first ZIP entry per EPUB spec
• replaceBelongsToCollection: EPUB3 uses belongs-to-collection with refines; EPUB2 uses calibre:series/calibre:series_index convention (widely supported by e-readers)
• addSubtitleToTitle: EPUB3 uses separate dc:title with title-type refinement; EPUB2 stores subtitle via booklore:subtitle metadata only (preserves round-trip fidelity)
• addBookloreMetadata / createBookloreMetaElement: EPUB3 uses property attribute with prefix; EPUB2 uses name/content attribute form. Also now writes booklore:subtitle for extraction round-trip.
• removeAllBookloreMetadata: Now handles both EPUB3 property and EPUB2 name attributes
• cleanupCalibreArtifacts: Preserves calibre:series and calibre:series_index metas (used for EPUB2 series)
• organizeMetadataElements: Correctly categorizes EPUB2-style series and booklore metas into their respective buckets
• Added isEpub3() helper method used throughout

Verification

Verified with epubcheck v5.3.0 — EPUB3 files modified by Booklore now produce 0 errors, 0 warnings.

Test Output

> Task :test
BUILD SUCCESSFUL in 41s
6 actionable tasks: 2 executed, 4 up-to-date

All 2570+ existing tests pass. 14 new tests added covering:

• EPUB3 creator metadata (meta refines for file-as, role with marc:relators scheme)
• EPUB2 creator metadata (opf: attributes, no EPUB3 constructs)
• Mimetype ZIP handling (stored first, no duplicates)
• EPUB3/EPUB2 series metadata
• EPUB3/EPUB2 subtitle handling
• EPUB3/EPUB2 booklore metadata format

[balazs-szucs]

Hi,

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