feat: OG link previews — track image + meta tags for Telegram/WhatsApp

- bincio/render/ogimage.py: generate 400x400 elevation-coloured PNG with Pillow
- bincio/serve/routers/ogimage.py: /activity/{id}/ OG HTML stub for bot UAs;
  /og-image/{user}/{id}.png serves pre-generated images with on-demand fallback
- scripts/generate_og_images.py: batch pre-generation, incremental (mtime skip)
- scripts/strava_elevation_audit.py: add source/threshold/MA columns and pct stats
- pyproject.toml: add Pillow>=10 to serve extras

scripts/generate_og_images.py

@@ -0,0 +1,91 @@
+"""Pre-generate OG track images for all activities.
+
+Writes 400×400 PNGs to {www_root}/og-image/{user}/{activity_id}.png.
+Skips activities that already have an up-to-date image (mtime check).
+Safe to run repeatedly — only processes new/changed activities.
+
+Usage:
+    uv run scripts/generate_og_images.py [--data-dir /var/bincio/data] [--www-root /var/www/activity]
+"""
+
+from __future__ import annotations
+
+import argparse
+import json
+import sys
+from pathlib import Path
+
+
+def generate_all(data_dir: Path, www_root: Path) -> None:
+    out_root = www_root / "og-image"
+    out_root.mkdir(parents=True, exist_ok=True)
+
+    from bincio.render.ogimage import generate
+
+    total = generated = skipped = errors = 0
+
+    users = sorted(
+        d.name for d in data_dir.iterdir()
+        if d.is_dir() and not d.name.startswith("_") and d.name != "segments"
+    )
+
+    for handle in users:
+        user_dir   = data_dir / handle
+        acts_dir   = user_dir / "activities"
+        img_dir    = out_root / handle
+        if not acts_dir.exists():
+            continue
+        img_dir.mkdir(exist_ok=True)
+        u_gen = u_skip = u_err = 0
+
+        for ts_path in sorted(acts_dir.glob("*.timeseries.json")):
+            activity_id = ts_path.name.replace(".timeseries.json", "")
+            out_path    = img_dir / f"{activity_id}.png"
+            total += 1
+
+            # Skip if image is newer than timeseries
+            if out_path.exists() and out_path.stat().st_mtime >= ts_path.stat().st_mtime:
+                skipped += 1
+                u_skip  += 1
+                continue
+
+            try:
+                ts      = json.loads(ts_path.read_text(encoding="utf-8"))
+                lat_arr = ts.get("lat") or []
+                lon_arr = ts.get("lon") or []
+                ele_arr = ts.get("elevation_m") or []
+                png     = generate(lat_arr, lon_arr, ele_arr)
+                out_path.write_bytes(png)
+                generated += 1
+                u_gen     += 1
+            except Exception as exc:
+                errors += 1
+                u_err  += 1
+                print(f"  ERROR {handle}/{activity_id}: {exc}", file=sys.stderr)
+
+        if u_gen or u_err:
+            print(f"{handle:<25} generated={u_gen:4d}  skipped={u_skip:4d}  errors={u_err}")
+        else:
+            print(f"{handle:<25} skipped={u_skip:4d} (all up to date)")
+
+    print(f"\nDone — {generated} generated, {skipped} skipped, {errors} errors  (total {total})")
+
+
+def main() -> None:
+    ap = argparse.ArgumentParser(description="Pre-generate OG track images")
+    ap.add_argument("--data-dir",  default="/var/bincio/data",   type=Path)
+    ap.add_argument("--www-root",  default="/var/www/activity",  type=Path)
+    args = ap.parse_args()
+
+    if not args.data_dir.exists():
+        print(f"ERROR: data dir not found: {args.data_dir}", file=sys.stderr)
+        sys.exit(1)
+
+    print(f"data-dir : {args.data_dir}")
+    print(f"www-root : {args.www_root}")
+    print(f"output   : {args.www_root}/og-image/\n")
+    generate_all(args.data_dir, args.www_root)
+
+
+if __name__ == "__main__":
+    main()