feat(reader): add fullscreen, keyboard shortcuts, search cancel, and go-to-percentage

[acx10]

📝 Description

Adds several usability improvements to the ebook reader: fullscreen mode, keyboard shortcuts help dialog, search cancellation, go-to-percentage input, and additional standard keyboard shortcuts.

🏷️ Type of Change

• New feature
• Enhancement to existing feature

🔧 Changes

• Fullscreen mode: Toggle via F key or header button, with Escape to exit
• Keyboard shortcuts help dialog: Press ? or click help icon in header to view all shortcuts
• Search cancellation: Cancel button on the search progress bar in the left panel
• Go-to-percentage input: Direct percentage input in the footer location popover with Enter/Go button
• New keyboard shortcuts: Space/Shift+Space (page navigation), Home/End (first/last section), T (TOC), S (search), N (notes)
• Sidebar toggle methods: T, S, N shortcuts toggle their respective panels open/closed
• Escape priority chain: Closes dialogs in order — shortcuts help → note dialog → controls → quick settings → metadata → fullscreen
• Shortcuts consistency: Removed non-standard vim keybindings (H/L) from both ebook and CBX readers; both readers now share the same standard shortcuts for common functions

🧪 Testing

• Open an EPUB in the reader
• Press F → enters fullscreen; press again → exits. Header button toggles icon
• Press ? → shortcuts help dialog opens; click "Got it" or press ?/Escape → closes
• Press Space/Shift+Space → navigates forward/backward
• Press Home/End → jumps to first/last section
• Press T → toggles TOC sidebar; S → search panel; N → notes panel
• Open search, type a query, observe progress bar → click cancel button → search stops
• Click percentage button in footer → popover opens → enter percentage → press Enter or click Go → reader jumps
• Press Escape → closes the topmost open dialog/panel

📸 Screenshots / Video (MANDATORY)

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✅ Pre-Submission Checklist

• Code follows project style guidelines and conventions
• Branch is up to date with develop (merge conflicts resolved)
• Automated tests added or updated to cover changes (backend and frontend)
• All tests pass locally (./gradlew test for backend, ng test for frontend)
• Changes manually verified in local dev environment (including related features)
• Screenshots or video proving the change works are attached above (MANDATORY)
• Flyway migration versioning is correct (if schema was modified)
• Documentation PR submitted to booklore-docs (if user-facing changes)
• PR is reasonably scoped (PRs over 1000+ changed lines will be closed, split into smaller PRs)

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💬 Additional Context (optional)

Both ebook and CBX readers now share the same standard keyboard shortcuts for common functions (arrows, Space, PageUp/PageDown, Home/End, F, Escape, ?). Reader-specific shortcuts (T/S/N for ebook panels, D/P for CBX direction/slideshow) remain unique to each reader.

[github-actions]

Frontend Test Results

8 tests  ±0   8 ✅ ±0   0s ⏱️ ±0s
2 suites ±0   0 💤 ±0 
1 files   ±0   0 ❌ ±0 

Results for commit 0b51af2. ± Comparison against base commit e8530fa.

[github-actions]

Backend Test Results

  233 files  ±0    233 suites  ±0   56s ⏱️ +3s
1 887 tests ±0  1 883 ✅ ±0  4 💤 ±0  0 ❌ ±0 
1 944 runs  ±0  1 940 ✅ ±0  4 💤 ±0  0 ❌ ±0 

Results for commit 0b51af2. ± Comparison against base commit e8530fa.

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$FieldOptions@de10870, enabledFields = null
org.booklore.service.metadata.MetadataRefreshServiceTest ‑ [3] fieldOptions = null, enabledFields = org.booklore.model.dto.request.MetadataRefreshOptions$EnabledFields@1fa0e7e5
org.booklore.service.metadata.MetadataRefreshServiceTest ‑ [4] fieldOptions = org.booklore.model.dto.request.MetadataRefreshOptions$FieldOptions@27b3a7bb, enabledFields = org.booklore.model.dto.request.MetadataRefreshOptions$EnabledFields@2d01a2e7

org.booklore.service.metadata.MetadataRefreshServiceTest ‑ [2] fieldOptions = org.booklore.model.dto.request.MetadataRefreshOptions$FieldOptions@3a2a8c5, enabledFields = null
org.booklore.service.metadata.MetadataRefreshServiceTest ‑ [3] fieldOptions = null, enabledFields = org.booklore.model.dto.request.MetadataRefreshOptions$EnabledFields@23bbdea3
org.booklore.service.metadata.MetadataRefreshServiceTest ‑ [4] fieldOptions = org.booklore.model.dto.request.MetadataRefreshOptions$FieldOptions@2d1855c3, enabledFields = org.booklore.model.dto.request.MetadataRefreshOptions$EnabledFields@7600c4f8