Clamp ebook gap on load to fix blank pages for v1 upgraders

[acx10]

Users who adjusted column gap in v1 had values stored as integers (5, 10, 15...) since the old +/- buttons incremented by 5. In v2 gap is a decimal fraction (0.05 = 5%), so those old values get interpreted as 500%+ which produces negative column gaps in the paginator math, collapsing the layout to blank pages. This just clamps the gap to the valid max of 0.5 when loading settings from the API.

Fixes #2863

[github-actions]

Frontend Test Results

413 tests  ±0   413 ✅ ±0   1s ⏱️ ±0s
  7 suites ±0     0 💤 ±0 
  1 files   ±0     0 ❌ ±0 

Results for commit 0e3e704. ± Comparison against base commit a97ada5.

[github-actions]

Backend Test Results

  336 files  ±0    336 suites  ±0   1m 35s ⏱️ +8s
2 492 tests ±0  2 477 ✅ ±0  15 💤 ±0  0 ❌ ±0 
2 549 runs  ±0  2 534 ✅ ±0  15 💤 ±0  0 ❌ ±0 

Results for commit 0e3e704. ± Comparison against base commit a97ada5.

This pull request removes 3 and adds 3 tests. Note that renamed tests count towards both.

org.booklore.service.metadata.MetadataRefreshServiceTest ‑ [2] fieldOptions = org.booklore.model.dto.request.MetadataRefreshOptions$FieldOptions@2268f9f1, enabledFields = null
org.booklore.service.metadata.MetadataRefreshServiceTest ‑ [3] fieldOptions = null, enabledFields = org.booklore.model.dto.request.MetadataRefreshOptions$EnabledFields@848a41f
org.booklore.service.metadata.MetadataRefreshServiceTest ‑ [4] fieldOptions = org.booklore.model.dto.request.MetadataRefreshOptions$FieldOptions@4374beee, enabledFields = org.booklore.model.dto.request.MetadataRefreshOptions$EnabledFields@783234a3

org.booklore.service.metadata.MetadataRefreshServiceTest ‑ [2] fieldOptions = org.booklore.model.dto.request.MetadataRefreshOptions$FieldOptions@2f7b2f85, enabledFields = null
org.booklore.service.metadata.MetadataRefreshServiceTest ‑ [3] fieldOptions = null, enabledFields = org.booklore.model.dto.request.MetadataRefreshOptions$EnabledFields@2c5b946b
org.booklore.service.metadata.MetadataRefreshServiceTest ‑ [4] fieldOptions = org.booklore.model.dto.request.MetadataRefreshOptions$FieldOptions@19d7b86e, enabledFields = org.booklore.model.dto.request.MetadataRefreshOptions$EnabledFields@215f3089