Add Enemies section: D&D stat-block table + detail/edit pages

- Enemy entity: full 5e stat block (size/type/subtype/alignment, AC, HP,
  speed, six ability scores, CR/XP/prof, saves/skills/senses/languages,
  damage & condition modifiers, traits/actions/bonus/reactions/legendary,
  description, source) plus a DM game-notes field and updated_at.
- CreatureSize / CreatureType enums.
- /enemies: server-side DataTable (name, size, type, CR, AC, HP, notes),
  "Add enemy" button.
- /enemies/{id}: stat block rendered read-only + editable game notes.
- /enemies/new and /enemies/{id}/edit: the full stat-block form (no notes).
- "Enemies" nav item between NPC's and Storyline.
- Table left empty on purpose.

Co-Authored-By: Claude Sonnet 5 <noreply@anthropic.com>

templates/base.html.twig

@@ -29,6 +29,7 @@
                             { route: 'app_home',      label: 'Overview' },
                             { route: 'app_characters', label: 'Characters' },
                             { route: 'app_npcs',      label: "NPC's" },
+                            { route: 'app_enemies',   label: 'Enemies' },
                             { route: 'app_storyline', label: 'Storyline' },
                         ] %}
                         <ul class="navbar-nav me-auto">