Feat: Replace Load More with Previous/Next pagination in library

Page size changes from 50 to 24. Library now shows discrete page navigation
with a "Page N of M" indicator, total image count, and URL state (?page=N)
so pages are bookmarkable and the browser Back button works. Tag filter
resets to page 1. Out-of-range page params are clamped silently.

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

specs/015-library-pagination/checklists/requirements.md

@@ -0,0 +1,34 @@
+# Specification Quality Checklist: Library Pagination UI
+
+**Purpose**: Validate specification completeness and quality before proceeding to planning
+**Created**: 2026-05-09
+**Feature**: [spec.md](../spec.md)
+
+## Content Quality
+
+- [X] No implementation details (languages, frameworks, APIs)
+- [X] Focused on user value and business needs
+- [X] Written for non-technical stakeholders
+- [X] All mandatory sections completed
+
+## Requirement Completeness
+
+- [X] No [NEEDS CLARIFICATION] markers remain
+- [X] Requirements are testable and unambiguous
+- [X] Success criteria are measurable
+- [X] Success criteria are technology-agnostic (no implementation details)
+- [X] All acceptance scenarios are defined
+- [X] Edge cases are identified
+- [X] Scope is clearly bounded
+- [X] Dependencies and assumptions identified
+
+## Feature Readiness
+
+- [X] All functional requirements have clear acceptance criteria
+- [X] User scenarios cover primary flows
+- [X] Feature meets measurable outcomes defined in Success Criteria
+- [X] No implementation details leak into specification
+
+## Notes
+
+- All items pass. Ready for `/speckit-plan`.