fix(admin): add missing article_stats route, 500 handler, dev debug mode

- Add /admin/articles/stats HTMX partial endpoint that was referenced
  by article_stats.html but never created (caused 500 during generation)
- Add @app.errorhandler(500) to log exceptions with traceback
- Switch dev_run.sh from Granian to Quart debug mode for browser
  tracebacks and auto-reload

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

CHANGELOG.md

@@ -8,6 +8,8 @@ The format is based on [Keep a Changelog](https://keepachangelog.com/en/1.1.0/).
 
 ### Fixed
 - **Admin template preview maps** — Leaflet maps rendered blank because `article-maps.js` called `L.divIcon()` at the IIFE top level before Leaflet was dynamically loaded, crashing the script. Moved `VENUE_ICON` creation into the `script.onload` callback so it runs after Leaflet is available. Previous commit's `.card` `overflow: visible` fix remains (clips tile layers otherwise).
+- **Admin articles page 500** — `/admin/articles` crashed with `BuildError` when an article generation task was running because `article_stats.html` partial referenced `url_for('admin.article_stats')` but the route didn't exist. Added the missing HTMX partial endpoint.
+- **Silent 500 errors in dev** — `dev_run.sh` used Granian which swallowed Quart's debug error pages, showing generic "Internal Server Error" with no traceback. Switched to `uv run python -m padelnomics.app` for proper debug mode with browser tracebacks. Added `@app.errorhandler(500)` to log exceptions even when running under Granian in production.
 - **Pipeline diagnostic script** (`scripts/check_pipeline.py`) — handle DuckDB catalog naming quirk where `lakehouse.duckdb` uses catalog `lakehouse` instead of `local`, causing SQLMesh logical views to break. Script now auto-detects the catalog via `USE`, and falls back to querying physical tables (`sqlmesh__<schema>.<table>__<hash>`) when views fail.
 - **Eurostat gas prices extractor** — `nrg_pc_203` filter missing `unit` dimension (API returns both KWH and GJ_GCV); now filters to `KWH`.
 - **Eurostat labour costs extractor** — `lc_lci_lev` used non-existent `currency` filter dimension; corrected to `unit: EUR`.