feat(photos): add a complete paged timeline and date scrubber

[veryCrunchy]

Parent epic: #14

User problem

Photos currently shows only a short recent slice instead of the user's complete photo and video history. Reaching an older month or year would require loading and scrolling through everything in order, and there is no date scrubber for fast navigation.

Goal

Provide a complete, performant chronological timeline with incremental paging and a draggable month/year scrubber similar to mature native photo galleries.

Scope

• replace the fixed recent-result cap with stable incremental timeline paging
• group media by meaningful day, month, and year sections
• add a touch-friendly vertical fast-scroll handle with a month/year preview while dragging
• provide accessible keyboard, pointer, and screen-reader alternatives to dragging
• jump to a date without downloading or decoding every intervening item
• keep scrolling and date jumps responsive while thumbnails, RAW enrichment, and metadata load
• deduplicate items consistently across page boundaries and refreshes
• preserve the logical grouping of RAW pairs and future motion/live-photo assets
• retain useful cached pages offline without treating a partial cache as the complete timeline
• support equivalent efficient navigation on desktop

Acceptance criteria

• a library larger than the current 80-item slice remains navigable from newest to oldest
• older pages load before the viewport reaches them without blocking navigation
• the scrubber exposes the current month and year and can jump across multiple years
• refreshes and overlapping server pages do not duplicate, reorder, or lose media
• cancellation, retry, empty months, timezone boundaries, and pre-1970 dates have deterministic tests
• rendering remains bounded for libraries containing thousands of items
• isolated visual QA fixtures cover short, long, loading, offline, and failed-page states
• Android emulator and desktop QA verify smooth scrolling and date navigation

Platforms

Android and desktop.