feat(admin): observability — job history, live now-analyzing, durations & metrics (0.84.0) (#6)

backend/migrations/0028_operation_metrics.sql

@@ -0,0 +1,39 @@
+-- Durable timing log for crawler operations + a duration column for page
+-- analysis. The dashboard's job history shows *what* ran; this records *how
+-- long it took* so operators can see per-operation durations and averages
+-- broken down by type/granularity (manga list walk, manga detail, cover,
+-- whole chapter — per-page crawl timing is derived from the chapter row's
+-- `items` count rather than stored per image).
+--
+-- This table is durable on purpose: it outlives the `crawler_jobs` done-job
+-- reaper so averages stay meaningful, and it captures the INLINE operations
+-- (list walk, manga detail, cover) that are not queue jobs at all. Volume is
+-- low (one row per manga / chapter / pass, not per image), so a generous
+-- retention reaper is hygiene rather than a necessity.
+CREATE TABLE crawl_metrics (
+    id          uuid PRIMARY KEY DEFAULT gen_random_uuid(),
+    -- Operation granularity. analyze_page is intentionally absent — analysis
+    -- duration lives on page_analysis.duration_ms (one row per page already).
+    op          text NOT NULL
+                    CHECK (op IN ('manga_list', 'manga_detail', 'manga_cover', 'chapter')),
+    -- Best-effort target context for labeling/drill. SET NULL so deleting a
+    -- manga/chapter doesn't erase its historical timings.
+    manga_id    uuid REFERENCES mangas(id) ON DELETE SET NULL,
+    chapter_id  uuid REFERENCES chapters(id) ON DELETE SET NULL,
+    outcome     text NOT NULL CHECK (outcome IN ('ok', 'failed')),
+    duration_ms bigint NOT NULL,
+    -- Unit count for the op: chapter = pages stored; manga_list = mangas
+    -- discovered. Drives the derived "per page" average. NULL when N/A.
+    items       integer,
+    error       text,
+    finished_at timestamptz NOT NULL DEFAULT now()
+);
+
+-- Per-type averages + the recent-ops log both filter by op and order by time.
+CREATE INDEX crawl_metrics_op_time_idx ON crawl_metrics (op, finished_at DESC);
+-- The window filter (last 24h / 7d / 30d) and the retention reaper scan by time.
+CREATE INDEX crawl_metrics_time_idx ON crawl_metrics (finished_at);
+
+-- Wall-clock the analysis worker spent on a page (vision dispatch). NULL for
+-- pre-existing rows and any page analyzed before this migration.
+ALTER TABLE page_analysis ADD COLUMN duration_ms bigint;