feat: Update reader template for foliate-js integration

Update reader page template to use foliate-js custom element and add theme selector UI.

Template Changes:
1. Add foliate-js integration:
   - Load foliate-themes.css for reading theme system
   - Load foliate-js/view.js to register <foliate-view> custom element
   - Replace <main id="reader-content"> with <foliate-view id="reader-view">
   - Foliate auto-initializes from the custom element

2. Add Reading Theme selector:
   - New section in settings panel (before Typography)
   - Single dropdown with 18 themes organized by category using <optgroup>
   - Categories: Classic Reading, Sky & Atmosphere, Sunset & Warmth, Nature & Earth, High Performance
   - Each theme shows descriptive name
   - Themes organized for easy discovery (grouped by mood/use case)

3. Remove broken references:
   - Remove ebook-content class (tied to broken CSS columns approach)
   - Clean up old reader-specific CSS class references

Reader Template Structure:
- Chrome (top/bottom bars): Back button, title, settings gear
- Bottom bar: Progress display, TOC/bookmarks/notes buttons, panel editor (comics)
- Settings panel: Chrome behavior, progress mode, reading themes, typography (fonts, spacing)
- TOC panel: Table of contents navigation
- Navigator panel: Page thumbnail with draggable viewport
- Bookmarks panel: User bookmarks with add button
- Dictionary popup: Word definition popup

Template Generator:
- Regenerated reader_templ.go via go generate
- Syncs template changes with Go backend

templates/reader.templ

@@ -11,6 +11,7 @@ templ Reader(user User, metadata ReaderMetadata, progress ReadingProgress, bookm
 			<title>{ metadata.Title } - Bookhoard Reader</title>
 			<link rel="manifest" href="/static/manifest.json"/>
 			<link href="/static/reader-fonts.css" rel="stylesheet"/>
+			<link href="/static/foliate-themes.css" rel="stylesheet"/>
 			<script src="/static/htmx.min.js"></script>
 			<script type="module" src="/static/reader.js"></script>
 			<link href="/static/style.css" rel="stylesheet"/>
@@ -45,9 +46,7 @@ templ Reader(user User, metadata ReaderMetadata, progress ReadingProgress, bookm
 					</div>
 				</div>
 			</div>
-			<main id="reader-content" tabindex="0" class="ebook-content w-full h-full">
-				<!-- Content loaded by JavaScript based on media type -->
-			</main>
+			<foliate-view id="reader-view"></foliate-view>
 			@DictionaryPopup()
 		</body>
 	</html>
@@ -135,6 +134,42 @@ templ ReaderSettingsPanel() {
 				</label>
 			</div>
 			<!-- Typography (ebooks only) -->
+			<div class="mb-6" data-visible-for="ebook">
+				<h3 class="font-semibold mb-2">Reading Theme</h3>
+				<label class="block mb-2">
+					<select name="reading_theme" class="w-full mt-1 px-3 py-2 rounded border">
+						<optgroup label="📖 Classic Reading">
+							<option value="light">Light</option>
+							<option value="paper">Paper</option>
+							<option value="sepia">Sepia</option>
+							<option value="parchment">Parchment</option>
+							<option value="warm">Warm</option>
+							<option value="candlelight">Candlelight</option>
+						</optgroup>
+						<optgroup label="🌤️ Sky & Atmosphere">
+							<option value="azure">Azure</option>
+							<option value="sky">Sky</option>
+							<option value="arctic">Arctic</option>
+							<option value="frost">Frost</option>
+						</optgroup>
+						<optgroup label="🌅 Sunset & Warmth">
+							<option value="dusk">Dusk</option>
+							<option value="sunset">Sunset</option>
+							<option value="twilight">Twilight</option>
+						</optgroup>
+						<optgroup label="🌲 Nature & Earth">
+							<option value="forest">Forest</option>
+							<option value="moss">Moss</option>
+							<option value="slate">Slate</option>
+						</optgroup>
+						<optgroup label="⚡ High Performance">
+							<option value="oled">OLED</option>
+							<option value="solarized">Solarized</option>
+						</optgroup>
+					</select>
+					<p class="text-xs mt-1" style="color: var(--text-secondary)">18 themes organized by category</p>
+				</label>
+			</div>
 			<div class="mb-6" data-visible-for="ebook">
 				<h3 class="font-semibold mb-2">Typography</h3>
 				<label class="block mb-2">