Lemenzo Gallery v1.6 - performance and memory hardening

Large-library performance
- Main gallery now requests MediaStore in 240-item pages and appends pages as the user approaches the end of the grid.
- Search no longer retains the complete media library; it scans bounded pages and keeps only matching results (maximum 2000 displayed results per search).
- Viewer loads a bounded media window around the requested item instead of keeping the entire library in memory.
- Album summaries aggregate page-by-page.
- Structured ContentResolver QUERY_ARG_LIMIT / QUERY_ARG_OFFSET are used, with a compatibility fallback for providers that reject Files paging.

Large-image safety
- Editor export now calculates a conservative bitmap working-set budget from the current process heap.
- Native source dimensions are retained when safe. Extremely large images are adaptively decoded only when required to prevent OOM/process death.
- Preview remains bounded independently from export.

Privacy Share
- JPEG metadata-free sharing is streaming and lossless with respect to compressed image pixels: EXIF/XMP/IPTC/comments and non-color application metadata are removed without a bitmap decode/re-encode.
- APP2 is preserved for ICC color profile continuity.
- PNG/WebP/other formats use a fresh memory-budgeted encode so inherited metadata is not carried over.

Video trim correctness
- The trim-start slider resolves to the previous video sync sample on release, matching the safe lossless MP4 mux boundary shown to the user.
- The muxer still avoids video recompression and can remove the audio track when Mute is selected.

Release gates
- No INTERNET permission.
- A successful build with `m LemenzoGallery` in the actual Android 16 LemenzoOS source tree is mandatory.
- Runtime/stress testing on target Pixel devices is mandatory before declaring production-final.