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)

helm/templates/secret.yaml

@@ -1,16 +0,0 @@
-{{- $secret := (lookup "v1" "Secret" .Release.Namespace (include "krawl.fullname" .)) -}}
-{{- $dashboardPath := "" -}}
-{{- if and $secret $secret.data -}}
-  {{- $dashboardPath = index $secret.data "dashboard-path" | b64dec -}}
-{{- else -}}
-  {{- $dashboardPath = printf "/%s" (randAlphaNum 32) -}}
-{{- end -}}
-apiVersion: v1
-kind: Secret
-metadata:
-  name: {{ include "krawl.fullname" . }}
-  labels:
-    {{- include "krawl.labels" . | nindent 4 }}
-type: Opaque
-stringData:
-  dashboard-path: {{ $dashboardPath | quote }}