Migrate configuration from environment variables to YAML file

- Add YAML-based configuration loaded from config.yaml (CONFIG_LOCATION env var)
  - Add PyYAML dependency and install requirements in Dockerfile
  - Replace Config.from_env() with get_config() singleton pattern
  - Remove server_header from config (now randomized from wordlists only)
  - Update docker-compose.yaml to mount config.yaml read-only
  - Update Helm chart: restructure values.yaml, generate config.yaml in ConfigMap
  - Update Kubernetes manifests: ConfigMap now contains config.yaml, deployments mount it
  - Remove Helm secret.yaml (dashboard path now auto-generated in config.yaml)

Dockerfile

@@ -4,6 +4,9 @@ LABEL org.opencontainers.image.source=https://github.com/BlessedRebuS/Krawl
 
 WORKDIR /app
 
+COPY requirements.txt /app/
+RUN pip install --no-cache-dir -r requirements.txt
+
 COPY src/ /app/src/
 COPY wordlists.json /app/