Add reset progress action for a candidate's quiz attempt, and modal-based candidate editing (#204)

* feat: add reset progress action for a candidate's quiz attempt

Admins previously had no way to let a candidate retake a quiz once
started. Adds a backoffice action that clears a candidate's given
answers and start timestamp for a quiz, closes #20.

* fix: wrap candidate progress reset in a transaction

Avoids leaving a candidate half-reset (answers deleted but started
still set) if the second flush fails. Addresses CodeRabbit review
comment on PR #204.

* feat: open candidate edit/add forms in modals with dirty-aware dismissal

Rename-candidate modal always blocked backdrop-click dismissal via a
hardcoded static backdrop; wire it into the existing bo--modal
controller so outside clicks/Escape only get blocked once the name
field has actually been edited. Also move "Add Candidate" from a
full-page navigation into the same turbo-frame modal pattern already
used for editing quiz questions, keeping the full-page form as a
fallback for non-JS/turbo requests.

* feat: show a hint for the candidates textarea and gate translations in CI

Add a help hint on the add-candidates form explaining one candidate per
line, and translate it plus a few strings from the earlier reset-progress
feature that had been missed. Also add a CI step that re-runs
translation:extract and fails the build if it produces uncommitted
changes, so untranslated/stale strings can't slip through review again.

* Just links

Justfile

@@ -61,9 +61,20 @@ up *args: init
 down *args:
     docker compose down --remove-orphans {{ args }}
 
-# Show the host ports assigned to this worktree (see `just init`)
+# Show the URLs (and DB connection) assigned to this worktree (see `just init`)
 ports:
-    @cat .env.local 2>/dev/null || echo "No .env.local yet, run 'just up' or 'just init' first."
+    #!/usr/bin/env bash
+    set -euo pipefail
+    if [ ! -f .env.local ]; then
+        echo "No .env.local yet, run 'just up' or 'just init' first."
+        exit 0
+    fi
+    set -a
+    source .env.local
+    set +a
+    echo "Tvdt:      https://localhost:${HTTPS_PORT}"
+    echo "Mailpit:   http://localhost:${MAILPIT_PORT}"
+    echo "Spotlight: http://localhost:${SPOTLIGHT_PORT}"
 
 stop:
     docker compose stop