feat: add featured/locked columns and auto-rotation logic to news pipeline

- Add `ai_grade`, `featured`, `featured_locked`, `landing_locked`, `author`, `article_published`, `image_url`, `has_unique_image` columns to news table
- Extend `news_images` schema with `alt_text`, `phash`, `width`, `height`, `is_placeholder` columns
- Create `idx_news_featured` index for efficient featured queries
- Update admin toggle endpoints to set `featured_locked`/`landing_locked` when manually toggling
- Propagate `featured` and `image_url` fields through landing page, news list, and detail page rendering
- Update `get_featured_news` to return `featured` and `image_url` fields
- Document in AGENTS.md the full zero-maintenance pipeline: image perceptual hashing, placeholder detection, AI grading on cleaned text, reliability gate, effective score computation, and post-loop landing rotation
- Update README.md service description to reflect automatic image comparison and landing rotation capabilities
- Clarify docs_api.py summaries that toggling featured/landing now locks articles from auto-rotation

tests/api/admin/aiusage/index.py

@@ -0,0 +1,41 @@
+# retoor <retoor@molodetz.nl>
+
+import time
+import requests
+from tests.conftest import BASE_URL
+from devplacepy.database import get_table, refresh_snapshot
+_counter_aiusage = [0]
+JSON_aiusage = {"Accept": "application/json"}
+def _db_user(name):
+    refresh_snapshot()
+    return get_table("users").find_one(username=name)
+def _admin_aiusage(seeded_db):
+    key = _db_user("alice_test")["api_key"]
+    s = requests.Session()
+    s.headers.update({"X-API-KEY": key})
+    return s
+
+
+def test_admin_ai_usage_page_requires_admin(app_server):
+    r = requests.get(f"{BASE_URL}/admin/ai-usage", allow_redirects=False)
+    assert r.status_code in (302, 401, 403)
+
+
+def test_admin_ai_usage_page_returns_html(app_server, seeded_db):
+    admin = _admin_aiusage(seeded_db)
+    r = admin.get(f"{BASE_URL}/admin/ai-usage")
+    assert r.status_code == 200
+    assert "AI usage" in r.text or "ai-usage" in r.text
+
+
+def test_admin_ai_usage_data_requires_auth(app_server):
+    r = requests.get(f"{BASE_URL}/admin/ai-usage/data", headers=JSON_aiusage)
+    assert r.status_code == 401
+
+
+def test_admin_ai_usage_data_returns_json(app_server, seeded_db):
+    admin = _admin_aiusage(seeded_db)
+    r = admin.get(f"{BASE_URL}/admin/ai-usage/data", headers=JSON_aiusage)
+    assert r.status_code == 200
+    data = r.json()
+    assert isinstance(data, dict)