switch llama-swap to unified-vulkan image with FLUX.1-dev image generation

- Update deployment to unified-vulkan-2026-05-19 (includes llama-server,
  sd-server, whisper-server in one image)
- Fix binary paths: /app/llama-server -> llama-server (now on PATH)
- Migrate groups -> matrix to allow FLUX to evict the always-on 0.8B model
  when image generation is requested
- Add FLUX.1-dev Q4_K_S model via sd-server
- Configure OpenWebUI image generation to use llama-swap sd-server
- Update renovate versioning regex to treat all unified-vulkan date tags as
  patch updates for automerge

apps/openwebui/release.yaml

@@ -74,3 +74,16 @@ spec:
         value: "false"
       - name: OAUTH_MERGE_ACCOUNTS_BY_EMAIL
         value: "true"
+      # Image generation via llama-swap sd-server
+      - name: ENABLE_IMAGE_GENERATION
+        value: "true"
+      - name: IMAGE_GENERATION_ENGINE
+        value: "openai"
+      - name: IMAGES_OPENAI_API_BASE_URL
+        value: "http://llama.llama.svc.cluster.local:11434/v1"
+      - name: IMAGES_OPENAI_API_KEY
+        value: "ignored"
+      - name: IMAGE_GENERATION_MODEL
+        value: "flux1-dev:Q4_K_S"
+      - name: IMAGE_SIZE
+        value: "512x512"