fix: Correct Alpine.js directive syntax in 4 template files

Fixed templ parsing errors caused by escaped quotes in Alpine.js @click
directives. The previous migration to @click used backslash-escaped
quotes (\") which templ cannot parse correctly.

Files affected:
- templates/api_explorer.templ:28 - Fixed missing <button> tag and quotes
- templates/collection_modal.templ:69,135 - Fixed color picker buttons (edit & create forms)
- templates/collections.templ:216 - Fixed remove book button
- templates/conflicts.templ:110 - Fixed resolve conflict button

Root cause: Commit 08d4561 converted onclick→@click but used escaped quotes
Fix: Replace all @click=\"function()\" with @click="function()"

This aligns with the standard Alpine.js pattern and fixes the 4 templ
generation errors reported in ESBUILD_MIGRATION_PLAN.md line 1168.

Resolves: Template parsing errors preventing build
Related: ESBUILD_MIGRATION_PLAN.md Phase 3 (Template Migration)

templates/collections.templ

@@ -213,7 +213,7 @@ templ CollectionDetail(user User, collection CollectionData, books []handlers.Bo
 							<!-- Remove Button -->
 							<div class="mt-3 pt-3 border-t" style="border-color: var(--border);">
 								<button
-									@click=\"removeBook('{ book.MediaItemID }')\"
+									@click="removeBook('{ book.MediaItemID }')"
 									class="px-3 py-1 text-sm border rounded hover:opacity-80"
 									style="border-color: var(--border); color: var(--text-secondary);"
 								>