deploy: sensible Dockerfile defaults + simplified compose snippet

Dockerfile now sets OLLAMA_URL=http://ollama:11434 and
RERANK_URL=http://llama-rerank:8080 as image defaults, assuming the
MCP container shares a Docker network with services named `ollama`
and `llama-rerank` (typical compose pattern). Drawbar's stack
already runs both — no cross-host IPs to maintain, no off-stack
GPU dependencies. Stays inside the trashpanda compose.

deploy/drawbar-compose-snippet.md simplified: no environment
overrides needed for the common case. Override block shown only
for stacks with non-default service names. Pull tag updated to
:corpus-2026.05.24.

Per the new architecture call:
- MCP doesn't reach out to cross-host Ollama instances (192.168.0.2,
  192.168.0.125 etc.) at serve time — only at index-build time in CI.
- All serve-time dependencies are in the same Docker network as
  the consumer apps.

Code push touches Dockerfile → image-only.yml will rebuild + push.
Future-me note: the image-only.yml needs Ollama reachable from the
Gitea Actions runner for the reindex step; that still uses the LAN
endpoints (workflow env), which is correct since indexing is CI-side
not serve-side.

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

Dockerfile

@@ -46,9 +46,13 @@ ENV PYTHONUNBUFFERED=1 \
     MCP_TRANSPORT=streamable-http \
     MCP_HOST=0.0.0.0 \
     MCP_PORT=8000 \
-    HYBRID_SEARCH=true
-    # RERANK_URL set at deploy time, e.g. http://llama-rerank:8080
-    # OLLAMA_URL set at deploy time, comma-separated list
+    HYBRID_SEARCH=true \
+    OLLAMA_URL=http://ollama:11434 \
+    RERANK_URL=http://llama-rerank:8080
+    # Defaults above assume the MCP container shares a Docker network
+    # with services named `ollama` and `llama-rerank`. Override either
+    # in the compose `environment:` block if your stack uses different
+    # service names or if you want to point at off-stack hosts.
 
 EXPOSE 8000