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/collection_rules.templ

@@ -11,7 +11,7 @@ templ CollectionRules(user User, collection CollectionData) {
 			<link href="/static/style.css" rel="stylesheet"/>
 			<link rel="icon" type="image/svg+xml" href="/static/favicon.svg"/>
 		</head>
-		<body class="theme-{ user.Theme }" x-data="collectionRules" x-init={ "initCollectionRules('" + collection.ID + "')" }>
+		<body class={ "theme-" + user.Theme } x-data="collectionRules" x-init={ "initCollectionRules('" + collection.ID + "')" }>
 			@Header(user, "/collections")
 			<div class="max-w-7xl mx-auto px-4 sm:px-6 lg:px-8 py-8">
 				<div class="mb-6">
@@ -20,7 +20,7 @@ templ CollectionRules(user User, collection CollectionData) {
 						Back to Collection
 					</button>
 					<div class="flex items-center gap-4">
-						<span class="grid place-items-center h-12 w-12 rounded-2xl shrink-0 text-2xl" style="background-color: var(--accent-muted); color: { collection.Color }">{ collection.Icon }</span>
+						<span class="grid place-items-center h-12 w-12 rounded-2xl shrink-0 text-2xl" style={ "background-color: var(--accent-muted); color: " + collection.Color }>{ collection.Icon }</span>
 						<div>
 							<h1 class="text-3xl font-bold" style="color: var(--text-primary)">{ collection.Name }</h1>
 							<p class="flex items-center gap-2" style="color: var(--text-secondary)">