add index endpoint

README.md

@@ -46,6 +46,39 @@ Response:
 }
 ```
 
+Index request (all discovered stations):
+
+```
+GET /api/pegel
+```
+
+Index request with limit:
+
+```
+GET /api/pegel?limit=5
+```
+
+Index response shape:
+
+```json
+{
+  "count": 5,
+  "total_available": 312,
+  "items": [
+    {
+      "station_id": "560021",
+      "station_title": "Golzern 1 / Vereinigte Mulde",
+      "source": "https://www.umwelt.sachsen.de/umwelt/infosysteme/hwims/portal/web/feed/wasserstand-pegel-560021"
+    }
+  ],
+  "source": "https://www.umwelt.sachsen.de/umwelt/infosysteme/hwims/portal/web/wasserstand-uebersicht",
+  "fetched_at": "2026-05-05T01:00:00+00:00",
+  "warnings": [
+    "optional, only present for partial failures"
+  ]
+}
+```
+
 ---
 
 ## 🚀 Local Development
@@ -62,6 +95,7 @@ uvicorn api.app:app --reload
 Open:
 
 ```
+http://127.0.0.1:8000/api/pegel
 http://127.0.0.1:8000/api/pegel/560021
 ```
 
@@ -109,6 +143,16 @@ Pegel ID is passed via URL:
 /api/pegel/<id>
 ```
 
+Index endpoint:
+
+```
+/api/pegel
+```
+
+Query params for index:
+
+ * `limit` (positive integer, optional; invalid values return HTTP 400)
+
 ---
 
 ## 📡 Data Source