feat: AI job tracking, range support, auto-prompt, and resume

- New `ai_jobs` PocketBase collection tracks all long-running AI tasks
  (batch-covers, chapter-names) with status, progress, and cancellation
- `handlers_aijobs.go`: GET/cancel endpoints for ai_jobs; centralised
  cancel registry (moved from handlers_catalogue)
- Batch-covers and chapter-names SSE handlers now create/resume ai_job
  records, support from_item/to_item ranges, and resume from items_done
  on restart via job_id
- New `POST /api/admin/image-gen/auto-prompt`: generates an image prompt
  from book description (cover) or chapter title (chapter) via LLM
- image-gen page: "Auto-prompt" button calls auto-prompt API when a slug
  is selected; falls back gracefully if TextGen not configured
- text-gen chapter-names: from/to chapter range inputs + job ID display
- catalogue-tools batch-covers: from/to item range + resume job ID input
- pb-init-v3.sh: adds ai_jobs collection (idempotent)

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

ui/src/routes/admin/text-gen/+page.svelte

@@ -80,6 +80,9 @@
 	let chAC = makeBookAC();
 	let chSlug = $state('');
 	let chPattern = $state(saved.chPattern ?? 'Chapter {n}: {scene}');
+	let chFromChapter = $state(0);
+	let chToChapter = $state(0);
+	let chJobID = $state('');
 	let chGenerating = $state(false);
 	let chError = $state('');
 
@@ -122,6 +125,7 @@
 		chBatchWarnings = [];
 		chApplySuccess = false;
 		chApplyError = '';
+		chJobID = '';
 
 		try {
 			const res = await fetch('/api/admin/text-gen/chapter-names', {
@@ -130,7 +134,9 @@
 				body: JSON.stringify({
 					slug: chSlug.trim(),
 					pattern: chPattern.trim(),
-					model: selectedModel
+					model: selectedModel,
+					from_chapter: chFromChapter || undefined,
+					to_chapter: chToChapter || undefined
 				})
 			});
 
@@ -161,6 +167,7 @@
 					if (!payload) continue;
 
 					let evt: {
+						job_id?: string;
 						batch?: number;
 						total_batches?: number;
 						chapters_done?: number;
@@ -176,6 +183,8 @@
 						continue;
 					}
 
+					if (evt.job_id) chJobID = evt.job_id;
+
 					if (evt.done) {
 						chBatchProgress = `Done — ${evt.total_chapters ?? chProposals.length} chapters`;
 						chGenerating = false;
@@ -579,6 +588,27 @@
 					</p>
 				</div>
 
+				<!-- Range (optional) -->
+				<div class="grid grid-cols-2 gap-3">
+					<div class="space-y-1">
+						<label class="text-xs font-medium text-(--color-muted) uppercase tracking-wide" for="ch-from">
+							From chapter <span class="font-normal">(0=all)</span>
+						</label>
+						<input id="ch-from" type="number" bind:value={chFromChapter} min="0"
+							class="w-full bg-(--color-surface-2) border border-(--color-border) rounded-lg px-3 py-2 text-(--color-text) text-sm focus:outline-none focus:ring-2 focus:ring-(--color-brand)" />
+					</div>
+					<div class="space-y-1">
+						<label class="text-xs font-medium text-(--color-muted) uppercase tracking-wide" for="ch-to">
+							To chapter <span class="font-normal">(0=all)</span>
+						</label>
+						<input id="ch-to" type="number" bind:value={chToChapter} min="0"
+							class="w-full bg-(--color-surface-2) border border-(--color-border) rounded-lg px-3 py-2 text-(--color-text) text-sm focus:outline-none focus:ring-2 focus:ring-(--color-brand)" />
+					</div>
+				</div>
+				{#if chJobID}
+					<p class="text-xs text-(--color-muted)">Job: <span class="font-mono">{chJobID}</span></p>
+				{/if}
+
 				<button
 					onclick={generateChapterNames}
 					disabled={!chCanGenerate}