fix: check response.ok before parsing JSON in fetch calls

Fix JSON parsing errors when server returns non-JSON responses:
- Check response.ok before calling response.json()
- Add fallback error messages using status text
- Apply fix to all fetch calls across 12 components

This prevents 'JSON.parse: unexpected character' errors when
server returns HTML error pages or other non-JSON responses.

src/components/ScheduleGenerator.tsx

@@ -25,14 +25,20 @@ export function ScheduleGenerator({ tournamentId, teamCount }: ScheduleGenerator
         method: "POST",
       })
 
-      const data = await response.json()
-
+      // Check response status first before parsing JSON
       if (!response.ok) {
-        setError(data.error || "Failed to generate schedule")
+        try {
+          const data = await response.json()
+          setError(data.error || "Failed to generate schedule")
+        } catch {
+          setError(`Failed to generate schedule: ${response.status} ${response.statusText}`)
+        }
         setIsGenerating(false)
         return
       }
 
+      const data = await response.json()
+
       setResult({
         roundsCreated: data.roundsCreated,
         matchupsCreated: data.matchupsCreated,
@@ -58,10 +64,13 @@ export function ScheduleGenerator({ tournamentId, teamCount }: ScheduleGenerator
         method: "DELETE",
       })
 
-      const data = await response.json()
-
       if (!response.ok) {
-        setError(data.error || "Failed to delete schedule")
+        try {
+          const data = await response.json()
+          setError(data.error || "Failed to delete schedule")
+        } catch {
+          setError(`Failed to delete schedule: ${response.status} ${response.statusText}`)
+        }
         setIsGenerating(false)
         return
       }