Fix console errors: React Router v7 flags, form a11y, bans 500

- Add v7_startTransition and v7_relativeSplatPath future flags to
  BrowserRouter to silence React Router deprecation warnings
- Add hidden autocomplete='username' inputs to LoginPage and SetupPage
  so password managers and browsers stop warning about missing username
  fields in password forms
- Mount fail2ban-dev-config volume into backend container at /config:ro
  so ban_service can open the fail2ban SQLite database returned by
  'get dbfile'; this fixes the 500 on GET /api/dashboard/bans
- Track compose.debug.yml in git (was previously untracked)

frontend/src/pages/LoginPage.tsx

@@ -129,6 +129,17 @@ export function LoginPage(): React.JSX.Element {
         )}
 
         <form onSubmit={(ev) => void handleSubmit(ev)}>
+          {/* Hidden username field — required by accessibility guidelines for
+              password managers to correctly identify the credential form. */}
+          <input
+            type="text"
+            autoComplete="username"
+            aria-hidden="true"
+            tabIndex={-1}
+            value="bangui"
+            readOnly
+            style={{ display: "none" }}
+          />
           <div className={styles.field}>
             <Field label="Password" required>
               <Input

frontend/src/pages/SetupPage.tsx

@@ -205,6 +205,17 @@ export function SetupPage(): React.JSX.Element {
         )}
 
         <form onSubmit={(ev) => void handleSubmit(ev)}>
+          {/* Hidden username field — required by accessibility guidelines for
+              password managers to correctly identify the credential form. */}
+          <input
+            type="text"
+            autoComplete="username"
+            aria-hidden="true"
+            tabIndex={-1}
+            value="bangui"
+            readOnly
+            style={{ display: "none" }}
+          />
           <div className={styles.fields}>
             <Field
               label="Master Password"