UX: remember last directory and zoom level; add support for jbig2/jpeg2000 to preview

[sam2kb]

• Remember chosen directory in File > Open across invocations, persisted to config.properties.
• Remember zoom level across document loads, persisted to config.properties.
• Add jbig2-imageio and jai-imageio-jpeg2000 dependencies so the PDF preview can render optimized/reduced-size PDFs.

[kwart]

Thanks for this @sam2kb! I pushed a follow-up commit (27c3779) with a few adjustments — quick summary of what changed and why:

Dropped jai-imageio-jpeg2000. The jbig2-imageio part is great and I kept it (Apache-2.0, and JBIG2 is common in scanned PDFs). But the JPEG2000 jar bundles the JJ2000 codec, which is under a restrictive license: it carries a patent warning, a field-of-use restriction ("no license for non JPEG 2000 conforming products"), and is explicitly GPL-incompatible. That is a poor fit for a project shipped under MPL-2.0 / LGPL-2.1. It would also have broken the release build in practice: the license-maven-plugin (add-third-party) allow-list only permits Apache-2.0/BSD/MIT/LGPL/MPL/BC, so a real (non-test) JJ2000 dependency trips failOnMissing/failOnBlacklist. JPEG2000 images in PDFs are rare, so the tradeoff didn't seem worth it. jai-imageio-core reverts to dependencyManagement-only (it was only there to feed the JPEG2000 codec / version convergence). JBIG2 licensing is picked up automatically by add-third-party, so no license-file changes are needed.

Persist view state less aggressively. The zoom listener was calling save() on every zoom change, i.e. synchronous disk I/O on the JavaFX thread per zoom step. I moved persistence to document-open and exit, keeping the zoom value in memory in between.

Persist last dir for all open paths. The last-directory save only happened on File > Open; drag-drop and recent-files went through openDocument() without persisting. Moved the save into openDocument() so all three paths remember the directory.

Minor: log persistence failures at FINE instead of swallowing exceptions, and tidied imports/constant placement.

The remember-directory and remember-zoom UX is a nice touch — thanks again!