docs(spec): add home redesign + CamGallery design

Home splits into 카메라 촬영 / 갤러리 불러오기 / 캠갤러리. Gallery import
uses the Photo Picker copied into app storage (no flatten). CamGallery
reads the existing Pictures/ClearCam MediaStore folder (saved items
only); items support view/share/OCR/delete. Reuses Result/Share/OCR.
minSdk 29 gives loadThumbnail + owner-based delete; zero permissions.

Constraint: no new persistence layer; zero runtime permissions kept.
Confidence: high
Scope-risk: module
Reversibility: moderate
Directive: user reviews spec, then writing-plans.
Tested: design self-review.
Not-tested: no code yet.
Related: 2026-05-30-clearcam-document-scanner-design.md

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