feat: add lossless page-tree mutation batches - #556

Summary

• add an atomic incremental page-tree mutation API for move, rotate, delete, duplicate, and cross-document page insertion
• preserve prior bytes, indirect identities, inherited page attributes, catalog semantics, xref style, and unrelated objects
• provide dry-run reports for replaced, added, and newly unreachable objects
• reject encrypted inputs, DocMDP-forbidden edits, dangling page references, and imports or duplicates that require unsupported AcroForm/tagged-PDF remapping
• reopen and validate temporary output before atomic publication

Validation

• cargo fmt --all -- --check
• cargo clippy -p oxidize-pdf --lib --test issue_538_page_tree_mutations_test -- -D warnings
• cargo test -p oxidize-pdf --test issue_538_page_tree_mutations_test
• ignored qpdf/Poppler interoperability test executed explicitly for classic xref tables and xref streams
• issue Add lossless page reordering that preserves the original object graph #531 lossless reorder and Enforce DocMDP certification permissions for incremental structural edits #532 DocMDP regression suites
• cargo test -p oxidize-pdf --lib: 6,765 passed, 3 ignored
• cargo test -p oxidize-pdf --doc: 215 passed, 26 ignored

Closes #538