docs(license): say what MIT here covers, and what it cannot

The code is mine to license; the schedules under fixtures/ and snapshots/
were compiled by wiki editors and describe events run by the publishers, so
relicensing them under MIT would be claiming something I never held. A reader
who forks this needs to know the data does not come with it.

Kept as a note under the unmodified MIT text rather than woven into it, so
the license itself still reads verbatim.

Co-Authored-By: Claude Opus 5 (1M context) <[email protected]>

LICENSE

@@ -19,3 +19,25 @@ AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
 LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
 OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
 SOFTWARE.
+
+---
+
+What the license above covers, and what it does not:
+
+The MIT license applies to the code in this repository — the server, the client,
+the parsers, the build and refresh scripts, and the documentation written for
+them. That is the part which is mine to license.
+
+It does not apply to the event data. The schedules, event names and event
+descriptions under `fixtures/` and `snapshots/`, and the feed built from them,
+were compiled by the editors of the sites they were fetched from — Game8,
+wiki.gg and the Arknights Wiki among them — and describe events run by the
+games' publishers. That material is not mine and is not relicensed here. It is
+checked in so the parsers can be tested against real pages, and it remains
+subject to whatever terms those sites and publishers set. If you reuse this
+project, the data is yours to obtain and attribute, not to inherit from me.
+
+Game names, event names, artwork and trademarks belong to their respective
+owners, including HoYoverse, Kuro Games, Hypergryph, Hotta Studio, Infold Games
+and Perfect World. This project is an unofficial fan-made tool, not endorsed by
+or affiliated with any of them or with any of the sources it reads.