Add inference-image MCP server (accessible image generation) + proper favicon sizes

- mcp/image_server.py: generate_image tool via the co-op gateway; per-member
  key injected through customUserVars (IC_API_KEY) -> env; verified standalone
  (handshake, tools/list, real 1024x1024 + 1536x1024 images, error paths)
- librechat.yaml: register inference-image with startup:false (per-user
  credentials), 120s timeout
- assets/: real favicon sizes (16/32/192), opaque apple-touch 180, padded
  maskable 512

librechat.yaml

@@ -160,11 +160,28 @@ webSearch:
   scraperProvider: "keenable"
   rerankerType: "none"
 
-# MCP servers (admin-configured). The docs server is the same stdlib-only
-# Python server Open WebUI uses; it lives on the persistent volume at
-# /app/data/mcp/server.py so it survives image updates.
+# MCP servers (admin-configured, on the persistent volume so they survive
+# image updates). Members opt in per conversation via the composer's +
+# palette; each user gets their own isolated server connection.
 mcpServers:
   inference-docs:
     command: /app/code/venv/bin/python3
     args: ["/app/data/mcp/server.py"]
     timeout: 60000
+  # Accessible image generation: one click in the + palette, no agent setup.
+  # Each member's own co-op key is injected per-user via customUserVars →
+  # env, so images bill to the member's own balance (chat-endpoint model).
+  inference-image:
+    command: /app/code/venv/bin/python3
+    args: ["/app/data/mcp/image_server.py"]
+    timeout: 120000
+    # Per-user credentials aren't available at boot; each member initializes
+    # their own connection after saving their key in the MCP panel.
+    startup: false
+    customUserVars:
+      IC_API_KEY:
+        title: "Inference Co-op API key"
+        description: "Your co-op API key — create one in the <a href='https://dashboard.inference.coop' target='_blank'>Member Dashboard</a>. Used for image generation; bills to your own balance."
+        sensitive: true
+    env:
+      IC_API_KEY: "{{IC_API_KEY}}"