Characters: seed the current party sheets, add skill expertise

The party sheets in assets/characters/ changed: Darrah_Oakwanderer.pdf is
gone, replaced by Darragh Fermwyr (same halfling ranger, renamed and
updated), Owayn Fermwyr (stout halfling fighter, BJ) and Dunnchadh
(ghostwise halfling druid, Circle of the Blighted, Rick).

- app:character:seed now carries those three sheets, read from the PDFs'
  form fields. Darragh's portrait is renamed to match his new name.
- New skill expertise field (double proficiency bonus), since Darragh's
  Deft Explorer gives him +7 Stealth and the sheet had nowhere to show
  it. Expertise implies proficiency; the sheet marks it with two dots,
  the edit form gets a checkbox list next to skill proficiencies.
- Migration adds skill_expertise, backfilling existing rows with [] so
  the NOT NULL JSON column works on tables that already have characters.

Tests: expertise math on the entity, and a catalog test that every seed
sheet hydrates into a Character that passes validation.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

templates/characters/_sheet.html.twig

@@ -60,8 +60,9 @@
                     <thead><tr><th>Skill</th><th>Abl.</th><th>Mod</th></tr></thead>
                     <tbody>
                         {% for skill, ability in constant('App\\Entity\\Character::SKILLS') %}
-                            <tr class="{{ c.isProficientInSkill(skill) ? 'is-proficient' }}">
-                                <td>{{ skill }}{{ c.isProficientInSkill(skill) ? ' ●' }}</td>
+                            {% set proficient = c.isProficientInSkill(skill) or c.hasExpertiseInSkill(skill) %}
+                            <tr class="{{ proficient ? 'is-proficient' }}">
+                                <td>{{ skill }}{{ c.hasExpertiseInSkill(skill) ? ' ●●' : (proficient ? ' ●') }}</td>
                                 <td>{{ ability|slice(0, 3) }}</td>
                                 <td>{{ sb.mod(c.skillModifier(skill)) }}</td>
                             </tr>

templates/characters/edit.html.twig

@@ -71,7 +71,8 @@
                     </div>
                     <div class="row">
                         <div class="col-md-4">{{ form_row(form.savingThrowProficiencies) }}</div>
-                        <div class="col-md-8">{{ form_row(form.skillProficiencies) }}</div>
+                        <div class="col-md-4">{{ form_row(form.skillProficiencies) }}</div>
+                        <div class="col-md-4">{{ form_row(form.skillExpertise) }}</div>
                     </div>
                 </div>
             </div>