Implement initial BookWyrm role

- Removed obsolete TODO.md
- Added config/main.yml with service, feature, CSP, and registration settings
- Added schema/main.yml defining vaulted SECRET_KEY (alphanumeric)
- Added tasks/main.yml to load stateful stack
- Added Dockerfile.j2 ensuring data/media dirs
- Added docker-compose.yml.j2 with application, worker, redis, volumes
- Added env.j2 with registration, secrets, DB, Redis, OIDC support
- Extended vars/main.yml with BookWyrm variables and OIDC, Docker, Redis settings
- Updated meta/main.yml with logo and run_after dependencies

Ref: https://chatgpt.com/share/68b6c060-3a0c-800f-89f8-e114a16a4a80

roles/web-app-bookwyrm/schema/main.yml

@@ -0,0 +1,6 @@
+credentials:
+  secret_key:
+    description: "Django SECRET_KEY for BookWyrm"
+    algorithm: "alphanumeric"   # uses generate_value('alphanumeric') → 64 random a-zA-Z0-9
+    validation:
+      min_length: 50            # Django recommends ≥50 characters