fix(templ): stop emitting literal { expr } text into attributes and body classes

templ does not interpolate { expr } inside quoted attribute values — the
braces ship as literal text (AGENTS.md gotcha #1). Swept every templ
source for the pattern and fixed all of it:

Body theme classes: 22 page bodies rendered class="theme-{ user.Theme }"
literally, so every page first-painted the :root default (Tokyo Night)
and flashed when main.js applied the real theme. All now render
class={ "theme-" + user.Theme } server-side.

Attribute interpolations (26 across 8 files):
- api_explorer: initAPIExplorerDoc path/body/response and the Copy
  Request/Response buttons (invalid JS, silently dead)
- collections: book-selection :checked/@change/@click ids and four
  hx-get search URLs (collection_id={ collection.ID })
- conflicts: Resolve button id
- devices: Kobo sync-url/auth-token element ids (copy lookups only
  worked because the id and the lookup were the same literal)
- unlinked_books: search-matches/manual-link clicks and container ids
- queue: status/priority badge classes never matched their CSS
- dashboard: Restore-section tooltip text
- collection_rules/collections: collection icon color

Free text goes through the new templates.JSONArg (json.Marshal) —
templ.JSONString in this templ version returns (string, error) and
cannot compose in attribute expressions; uuids via device.ID.String().
Includes regen-only drift from running templ generate (error-path
normalization) on files with no source change.

templates/api_explorer.templ

@@ -28,18 +28,18 @@ templ APIExplorer(explorer APIExplorerData) {
 				<pre class="card p-4 overflow-x-auto"><code class="text-sm" style="color: var(--text-primary);">{ explorer.Endpoint.Response }</code></pre>
 			</div>
 			<div class="flex gap-2">
-				<button @click="copyToClipboard(JSON.stringify({ explorer.Endpoint.RequestBody }, null, 2))" class="btn btn-secondary text-sm">
+				<button @click={ "copyToClipboard(" + JSONArg(explorer.Endpoint.RequestBody) + ")" } class="btn btn-secondary text-sm">
 					@Icon("copy", "h-4 w-4")
 					Copy Request
 				</button>
-				<button @click="copyToClipboard(JSON.stringify({ explorer.Endpoint.Response }, null, 2))" class="btn btn-secondary text-sm">
+				<button @click={ "copyToClipboard(" + JSONArg(explorer.Endpoint.Response) + ")" } class="btn btn-secondary text-sm">
 					@Icon("copy", "h-4 w-4")
 					Copy Response
 				</button>
 			</div>
 		</div>
 	} else {
-		<div class="card p-6 mt-8 space-y-5" x-data="apiExplorerDoc" x-init="initAPIExplorerDoc('{ explorer.Endpoint.Path }', '{ explorer.Endpoint.RequestBody }', '{ explorer.Endpoint.Response }')">
+		<div class="card p-6 mt-8 space-y-5" x-data="apiExplorerDoc" x-init={ "initAPIExplorerDoc(" + JSONArg(explorer.Endpoint.Path) + ", " + JSONArg(explorer.Endpoint.RequestBody) + ", " + JSONArg(explorer.Endpoint.Response) + ")" }>
 			<div class="flex items-center gap-2 flex-wrap">
 				if explorer.Endpoint.Method == "GET" {
 					<span class="badge status-completed">{ explorer.Endpoint.Method }</span>