infra: swap hobby PG to timescaledb-ha + bump CH max_concurrent_queries to 50 (HOL-35)

[BrewingCoder]

Summary

Two related infra tweaks surfaced during HOL-26 / HOL-29 prep work, plus a Dockerfile fix.

1. Hobby PG image: ankane/pgvector → timescale/timescaledb-ha:pg16

Hobby PG image swaps to bundle TimescaleDB + pgvector + timescaledb_toolkit. The new image enables hypertable partitioning + drop_chunks retention for HOL-29's high-volume analytics tables (logs, traces, error_objects, sessions). Apache 2 base + Timescale License community features; AGPL-compatible.

Volume layout note: timescaledb-ha lays its data dir at /home/postgres/pgdata/data, NOT the upstream /var/lib/postgresql/data. Updated the volume mount to match. Anyone swapping back to a different PG image needs to revert that path too — flagged in compose.yml comment.

One-time data wipe: the path change means existing dev volumes don't carry forward. DevSeed recreates 5 workspaces + 5 projects on first start (verified). Production deployments would need a pg_dump/restore migration plan.

2. CH max_concurrent_queries 20 → 50

HOL-24 set this to 20 to constrain idle. Real workload exceeded it — single SHOW CREATE TABLE queries got rejected with "Too many simultaneous queries" during HOL-29 schema-discovery, because the backend's six worker hosted services keep CH busy continuously. 50 is still well below the default of 100. Insert/select sub-caps bumped 10 → 25 each.

3. Dockerfile fix (uncovered while live-testing the above)

backend-dotnet.Dockerfile only had COPY directives for projects that existed before HOL-25/26. The new HoldFast.Analytics and HoldFast.Data.Postgres projects were missing from the pre-restore COPY block, so dotnet restore couldn't generate their assets files and the publish step failed. Added the two missing lines + a comment reminding future contributors to update this list when adding projects to the slnx.

Acceptance verified live

• docker compose up -d brings up TimescaleDB-HA cleanly with the corrected volume mount
• DevSeed recreates 5 workspaces + 5 projects in the new image
• HOL-26 PG migrations now actually run on backend startup:
  Analytics PG migration: applying 1 0001_create_analytics_schema.up.sql Analytics PG migration: applying 2 0002_create_schema_migrations.up.sql Analytics PG migration: applying 3 0003_install_extensions.up.sql Analytics PG migrations: 3 applied, 3 total, 0 already-applied
• analytics.schema_migrations populated with versions 1–3, all dirty=false
• TimescaleDB 2.26.4 extension active (vs. the NOTICE-no-op in the old image)
• CH max_concurrent_queries reads 50 from system.server_settings
• Backend /health 200; existing CH backend untouched

Stats

4 files changed, +27 / -8.

Closes HOL-35.

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