feat(pipeline): tests, docs, and ruff fixes (subtask 6/6)

- Add 29-test suite for all pipeline routes, data helpers, and query
  execution (test_pipeline.py); all 1333 tests pass
- Fix ruff UP041: asyncio.TimeoutError → TimeoutError in analytics.py
- Fix ruff UP036/F401: replace sys.version_info tomllib block with
  plain `import tomllib` (project requires Python 3.11+)
- Fix ruff F841: remove unused `cutoff` variable in pipeline_overview
- Update CHANGELOG.md with Pipeline Console entry
- Update PROJECT.md: add Pipeline Console to Admin Panel done list

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

PROJECT.md

@@ -114,6 +114,7 @@
 - [x] **Admin email gallery** (`/admin/emails/gallery`) — card grid of all templates, EN/DE preview in sandboxed iframe, "View in sent log" cross-link; compose page now has HTMX live preview pane
 - [x] **pSEO Engine tab** (`/admin/pseo`) — content gap detection, data freshness signals, article health checks (hreflang orphans, missing build files, broken scenario refs), generation job monitoring with live progress bars
 - [x] **Marketplace admin dashboard** (`/admin/marketplace`) — lead funnel, credit economy, supplier engagement, live activity stream, inline feature flag toggles
+- [x] **Pipeline Console** (`/admin/pipeline`) — 4-tab operational dashboard: extraction status grid per source, filterable run history with stale-run management ("Mark Failed"), data catalog with column schema + 10-row sample, SQL query editor with dark-themed textarea + schema sidebar + read-only security sandboxing (keyword blocklist, 10s timeout, 1,000-row cap)
 - [x] **Lead matching notifications** — `notify_matching_suppliers` task on quote verification + `send_weekly_lead_digest` every Monday; one-click CTA token in forward emails
 - [x] **Migration 0022** — `status_updated_at`, `supplier_note`, `cta_token` on `lead_forwards`; supplier respond endpoint; inline HTMX lead detail actions; extended quote form fields