fix: chain providers, i18n, dedup isWebRuntime, and a11y label

Conditionally build `chainProviders` so empty `urls` arrays are never passed downstream. Replace hardcoded "Chain ticker: " with `capitalize(t('chain_ticker'))` and add the translation key to all locales. Remove the duplicate `isWebRuntime` in `media-hosting-settings.tsx` in favor of the shared implementation in `show-upload-controls`. Add `aria-label` to the directory codes input in `TopbarEditModal`.

src/components/settings-modal/crypto-wallets-setting/crypto-wallets-setting.tsx

@@ -102,7 +102,7 @@ const CryptoWalletsForm = ({ account }: { account: Account | undefined }) => {
     walletsArray.length > 0 ? (
       <div key={selectedWallet} className={styles.walletBox}>
         <div className={`${styles.walletField} ${styles.step1}`}>
-          <span className={styles.walletFieldTitle}>Chain ticker: </span>
+          <span className={styles.walletFieldTitle}>{capitalize(t('chain_ticker'))}: </span>
           <input
             type='text'
             onChange={(e) => setWalletsArrayProperty(selectedWallet, 'chainTicker', e.target.value)}