feat(analysis): enqueue page-analysis on upload/crawl + admin backfill endpoints

Wires the analyze_page job kind into the page-create paths and adds admin
controls, all gated on a new ANALYSIS_ENABLED flag (AppState.analysis_enabled,
config::AnalysisConfig):

- Chapter upload (api::chapters) enqueues one analyze_page job per page
  after the tx commits (best-effort; failures logged, never fatal).
- Crawler content sync (persist_pages → RETURNING id) enqueues per
  persisted page when the daemon dispatcher's analysis_enabled flag is set;
  threaded through sync_chapter_content (CLI/resync pass false).
- repo::page_analysis::enqueue_all_pages: bulk backfill via INSERT..SELECT,
  skipping done pages (only_unanalyzed) and existing pending jobs.
- New admin endpoints (RequireAdmin, 503 when disabled, audited):
  POST /admin/analysis/reenqueue and POST /admin/pages/:id/analyze (force).

Tests: upload enqueues N jobs / no-op when disabled; crawler persist_pages
enqueue gate; admin reenqueue (backfill, idempotent, only-unanalyzed, 503,
non-admin 403) and force-analyze (force flag, 404).

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

backend/src/app.rs

@@ -56,6 +56,11 @@ pub struct AppState {
     /// `Arc` keeps the clone cheap. Empty list → check is skipped
     /// (operator opt-out documented in `.env.example`).
     pub admin_allowed_origins: Arc<Vec<String>>,
+    /// When `true`, page-create paths (upload + crawler) enqueue
+    /// `analyze_page` jobs and the admin re-enqueue endpoints are active.
+    /// Mirrors `config.analysis.enabled`; defaults to `false` so the
+    /// feature is opt-in and the test harness inherits a no-op gate.
+    pub analysis_enabled: bool,
 }
 
 /// Shared handle the admin crawler endpoints use to observe and control
@@ -113,7 +118,13 @@ pub async fn build(config: Config) -> anyhow::Result<AppHandle> {
     let storage: Arc<dyn Storage> = Arc::new(LocalStorage::new(config.storage_dir.clone()));
 
     let (daemon, resync, crawler) = if config.crawler.daemon_enabled {
-        let spawned = spawn_crawler_daemon(db.clone(), Arc::clone(&storage), &config.crawler).await?;
+        let spawned = spawn_crawler_daemon(
+            db.clone(),
+            Arc::clone(&storage),
+            &config.crawler,
+            config.analysis.enabled,
+        )
+        .await?;
         (Some(spawned.handle), Some(spawned.resync), Some(spawned.crawler))
     } else {
         tracing::info!("crawler daemon disabled (CRAWLER_DAEMON=false)");
@@ -130,6 +141,7 @@ pub async fn build(config: Config) -> anyhow::Result<AppHandle> {
         resync,
         crawler,
         admin_allowed_origins: Arc::new(config.admin_allowed_origins.clone()),
+        analysis_enabled: config.analysis.enabled,
     };
     let router = router(state).layer(cors_layer(&config.cors_allowed_origins));
     Ok(AppHandle { router, daemon })
@@ -149,6 +161,7 @@ async fn spawn_crawler_daemon(
     db: PgPool,
     storage: Arc<dyn Storage>,
     cfg: &CrawlerConfig,
+    analysis_enabled: bool,
 ) -> anyhow::Result<SpawnedDaemon> {
     // Reqwest client with a shared cookie jar so CDN image fetches include
     // PHPSESSID. The same `Arc<Jar>` is held by the SessionController, so a
@@ -288,6 +301,7 @@ async fn spawn_crawler_daemon(
         rate: Arc::clone(&rate),
         download_allowlist: cfg.download_allowlist.clone(),
         max_image_bytes: cfg.max_image_bytes,
+        analysis_enabled,
         transient_failures: Arc::new(AtomicU32::new(0)),
         restart_threshold: cfg.browser_restart_threshold,
         drain_deadline: cfg.job_timeout,
@@ -446,6 +460,9 @@ struct RealChapterDispatcher {
     rate: Arc<HostRateLimiters>,
     download_allowlist: DownloadAllowlist,
     max_image_bytes: usize,
+    /// Enqueue `analyze_page` jobs for freshly-crawled pages. Mirrors
+    /// `config.analysis.enabled`.
+    analysis_enabled: bool,
     /// Consecutive transient chapter failures; resets on any success.
     /// Drives the automatic coordinated browser restart.
     transient_failures: Arc<std::sync::atomic::AtomicU32>,
@@ -501,6 +518,7 @@ impl ChapterDispatcher for RealChapterDispatcher {
                     self.max_image_bytes,
                     self.tor.as_deref(),
                     Some(&self.status),
+                    self.analysis_enabled,
                 )
                 .await;
                 drop(lease);