fix: export_serving — Arrow-based copy, rename to analytics.duckdb

Two bugs fixed:

1. Cross-connection COPY: DuckDB doesn't support referencing another
   connection's tables as src.serving.table. Replace with Arrow as
   intermediate: src reads to Arrow, dst.register() + CREATE TABLE.

2. Catalog/schema name collision: naming the export file serving.duckdb
   made DuckDB assign catalog name "serving" — same as the schema we
   create inside it. Every serving.table query became ambiguous. Rename
   to analytics.duckdb (catalog "analytics", schema "serving" = no clash).

   SERVING_DUCKDB_PATH values updated: serving.duckdb → analytics.duckdb
   in supervisor, service, bootstrap, dev_run.sh, .env.example, docker-compose.

3. Temp file: use _export.duckdb (not serving.duckdb.tmp) to avoid
   the same catalog collision during the write phase.

Verified: 6 tables exported, serving.* queries work read-only.

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

web/docker-compose.yml

@@ -10,7 +10,7 @@ services:
     env_file: .env
     environment:
       - DATABASE_PATH=/app/data/app.db
-      - SERVING_DUCKDB_PATH=/app/duckdb/serving.duckdb
+      - SERVING_DUCKDB_PATH=/app/duckdb/analytics.duckdb
     healthcheck:
       test: ["CMD", "curl", "-f", "http://localhost:5000/health"]
       interval: 30s