Add Docker support and refactor prompt/queue internals

- Add Dockerfile, docker-compose.yml, .dockerignore for containerised deployment
- Extract _resolve_character(), _ensure_character_fields(), _append_background() helpers to eliminate repeated inline character-field injection and background-tag patterns across all secondary-category generate routes
- Add _IDENTITY_KEYS / _WARDROBE_KEYS constants
- Fix build_extras_prompt() bug: detailer prompt (a list) was being appended as a single item instead of extended
- Replace all per-route _finalize closures with _make_finalize() factory, reducing duplication across 10 generate routes
- Add _prune_job_history() called each worker loop iteration to prevent unbounded memory growth
- Remove 10 orphaned legacy finalize_generation HTTP routes and check_status route (superseded by job queue API since job-queue branch)
- Remove one-time migration scripts (migrate_actions, migrate_detailers, migrate_lora_weight_range, migrate_wardrobe)
- Update CLAUDE.md and README.md to document new helpers, queue architecture, and Docker deployment

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

Dockerfile

@@ -0,0 +1,29 @@
+FROM python:3.12-slim
+
+# Install system deps: git (for danbooru-mcp repo clone) + docker CLI
+RUN apt-get update && apt-get install -y --no-install-recommends \
+    git \
+    curl \
+    ca-certificates \
+    && install -m 0755 -d /etc/apt/keyrings \
+    && curl -fsSL https://download.docker.com/linux/debian/gpg -o /etc/apt/keyrings/docker.asc \
+    && chmod a+r /etc/apt/keyrings/docker.asc \
+    && echo "deb [arch=$(dpkg --print-architecture) signed-by=/etc/apt/keyrings/docker.asc] https://download.docker.com/linux/debian $(. /etc/os-release && echo "$VERSION_CODENAME") stable" \
+       > /etc/apt/sources.list.d/docker.list \
+    && apt-get update && apt-get install -y --no-install-recommends docker-ce-cli docker-compose-plugin \
+    && rm -rf /var/lib/apt/lists/*
+
+WORKDIR /app
+
+COPY requirements.txt .
+RUN pip install --no-cache-dir -r requirements.txt
+
+COPY . .
+
+# Writable dirs that will typically be bind-mounted at runtime
+RUN mkdir -p static/uploads instance flask_session data/characters data/clothing \
+    data/actions data/styles data/scenes data/detailers data/checkpoints data/looks
+
+EXPOSE 5000
+
+CMD ["python", "app.py"]