fix(image-render): F6 ReliableQueue 적용 (F6 part 5)

- worker.py: poll_once + ReliableQueue + startup recovery
- 3 provider (gpt_image/nano_banana/flux) dispatch table 보존
- Dockerfile: build context=services/, _shared 포함, PYTHONPATH=/app
- docker-compose.yml: image-render build context 갱신

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

services/image-render/providers/flux_workflow.json

@@ -0,0 +1,83 @@
+{
+  "5": {
+    "inputs": {
+      "width": 1024,
+      "height": 1024,
+      "batch_size": 1
+    },
+    "class_type": "EmptyLatentImage",
+    "_meta": {"title": "Empty Latent Image"}
+  },
+  "6": {
+    "inputs": {
+      "text": "%PROMPT%",
+      "clip": ["11", 0]
+    },
+    "class_type": "CLIPTextEncode",
+    "_meta": {"title": "Positive Prompt"}
+  },
+  "8": {
+    "inputs": {
+      "samples": ["13", 0],
+      "vae": ["10", 0]
+    },
+    "class_type": "VAEDecode",
+    "_meta": {"title": "VAE Decode"}
+  },
+  "9": {
+    "inputs": {
+      "filename_prefix": "flux",
+      "images": ["8", 0]
+    },
+    "class_type": "SaveImage",
+    "_meta": {"title": "Save Image"}
+  },
+  "10": {
+    "inputs": {
+      "vae_name": "ae.safetensors"
+    },
+    "class_type": "VAELoader",
+    "_meta": {"title": "Load VAE"}
+  },
+  "11": {
+    "inputs": {
+      "clip_name1": "clip_l.safetensors",
+      "clip_name2": "t5xxl_fp8_e4m3fn.safetensors",
+      "type": "flux"
+    },
+    "class_type": "DualCLIPLoader",
+    "_meta": {"title": "Dual CLIP Loader"}
+  },
+  "12": {
+    "inputs": {
+      "unet_name": "flux1-schnell-fp8.safetensors",
+      "weight_dtype": "default"
+    },
+    "class_type": "UNETLoader",
+    "_meta": {"title": "Load Diffusion Model"}
+  },
+  "13": {
+    "inputs": {
+      "seed": 0,
+      "steps": 4,
+      "cfg": 1.0,
+      "sampler_name": "euler",
+      "scheduler": "simple",
+      "denoise": 1.0,
+      "model": ["12", 0],
+      "positive": ["6", 0],
+      "negative": ["33", 0],
+      "latent_image": ["5", 0]
+    },
+    "class_type": "KSampler",
+    "_meta": {"title": "KSampler"}
+  },
+  "33": {
+    "inputs": {
+      "text": "",
+      "clip": ["11", 0]
+    },
+    "class_type": "CLIPTextEncode",
+    "_meta": {"title": "Negative Prompt (empty for Schnell)"}
+  }
+}