Soft-delete + source-count diagnostics; thesis v4 (0.1.0:47)

- DELETE handlers soft-delete (set deleted_at) + cascade contact -> opps/comms/lp
  instead of hard-deleting (guardrail #3); list queries filter deleted rows.
- ingest: chunking excludes soft-deleted records; qdrant delete-by-source-id;
  sync prunes soft-deleted records' vectors incrementally.
- /api/system/status returns raw source-record counts for sanity-checking.
- docs/thesis-seed-v4.md (no "bet" language, scarcity-forward, freedom-tech as
  a banner option, tightened pillars, reworked segments + edge).

Soft-delete verified via the running HTTP server (delete -> hidden + row kept).

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

backend/ingest/qdrant_io.py

@@ -48,3 +48,16 @@ def upsert(points):
 def count():
     status, data = _req("POST", f"/collections/{COL}/points/count", {"exact": True})
     return (data or {}).get("result", {}).get("count")
+
+
+def delete_by_source_ids(source_ids):
+    """Delete all chunks belonging to the given CRM source records (by payload
+    source_id) — used to prune soft-deleted records from the index."""
+    ids = list(source_ids)
+    if not ids:
+        return None
+    status, data = _req("POST", f"/collections/{COL}/points/delete?wait=true",
+                        {"filter": {"must": [{"key": "source_id", "match": {"any": ids}}]}})
+    if status not in (200, 201):
+        raise RuntimeError(f"delete points -> {status}: {data}")
+    return data