fix(adsb): update Planespotters User-Agent to include contact URL

Planespotters.net now requires a descriptive User-Agent with a contact
URL or email — generic strings return 403. Updated to comply with their
API policy.

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

routes/adsb.py

@@ -1786,7 +1786,9 @@ def aircraft_photo(registration: str):
     try:
         # Planespotters.net public API
         url = f"https://api.planespotters.net/pub/photos/reg/{registration}"
-        resp = requests.get(url, timeout=5, headers={"User-Agent": "INTERCEPT-ADS-B/1.0"})
+        resp = requests.get(
+            url, timeout=5, headers={"User-Agent": "INTERCEPT-ADS-B/2.27 (+https://github.com/smittix/intercept)"}
+        )
 
         if resp.status_code == 200:
             data = resp.json()