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/app/admin/matches/upload/page.tsx

@@ -93,13 +93,15 @@ export default function UploadMatchesPage() {
           eventDate: new Date().toISOString(),
         }),
       })
-      const data = await response.json()
-      if (response.ok && data.tournament) {
-        const newTournaments = [data.tournament]
-        setTournaments(newTournaments)
-        setSelectedTournament(data.tournament.id.toString())
-        setManualTournament(data.tournament.id.toString())
-        return data.tournament
+      if (response.ok) {
+        const data = await response.json()
+        if (data.tournament) {
+          const newTournaments = [data.tournament]
+          setTournaments(newTournaments)
+          setSelectedTournament(data.tournament.id.toString())
+          setManualTournament(data.tournament.id.toString())
+          return data.tournament
+        }
       }
       return null
     } catch (err) {
@@ -155,12 +157,20 @@ export default function UploadMatchesPage() {
         body: formData,
       })
 
-      const data = await response.json()
-
       if (!response.ok) {
-        throw new Error(data.error || "Failed to upload CSV")
+        try {
+          const errorData = await response.json()
+          throw new Error(errorData.error || "Failed to upload CSV")
+        } catch (jsonError) {
+          if (jsonError instanceof Error && jsonError.message !== "Failed to upload CSV") {
+            throw jsonError
+          }
+          throw new Error(`Failed to upload CSV: ${response.status} ${response.statusText}`)
+        }
       }
 
+      const data = await response.json()
+
       setCsvSuccess(
         `Successfully imported ${data.importedCount} matches. ` +
         `${data.errorCount || 0} errors occurred.` +
@@ -262,12 +272,20 @@ export default function UploadMatchesPage() {
         body: JSON.stringify({ matches: matchesData }),
       })
 
-      const data = await response.json()
-
       if (!response.ok) {
-        throw new Error(data.error || "Failed to create matches")
+        try {
+          const errorData = await response.json()
+          throw new Error(errorData.error || "Failed to create matches")
+        } catch (jsonError) {
+          if (jsonError instanceof Error && jsonError.message !== "Failed to create matches") {
+            throw jsonError
+          }
+          throw new Error(`Failed to create matches: ${response.status} ${response.statusText}`)
+        }
       }
 
+      const data = await response.json()
+
       setManualSuccess(
         `Successfully created ${data.importedCount} matches. ` +
         `${data.errorCount || 0} errors occurred.` +