Feature/postgres cdc multi schema

[ness-david-dedu]

• Multi-schema replication — schema field now accepts a glob pattern (e.g. tenant_*) in addition to an exact name. All matching schemas are replicated through a single replication slot and publication,
  removing the need for one slot per tenant.
• commit_ts_ms metadata — transaction commit timestamp (Unix milliseconds) sourced from the WAL BEGIN record; available on all live CDC messages (insert/update/delete), cleared on COMMIT to prevent stale
  state leaking into subsequent transactions.
• before metadata — JSON-encoded pre-image of the row for update and delete operations. Populated from OldTuple when REPLICA IDENTITY FULL is set on the table; nil for inserts and snapshot reads.
• pg_schema metadata — schema name of the originating table, useful for per-tenant routing downstream.
• Bug fix — validateSchemaPattern accepted "" (empty quoted identifier, length 2) due to an off-by-one; corrected to require at least one character inside the quotes.

[squiidz]

Re-reviewed after the rebase — the critical issue from the earlier pass is resolved: stream_message.go and replication_message_decoders.go are no longer touched, so the duplicate CommitTs/Before/tuple-decoding reimplementation (which had drifted from what main already shipped in #4554/#4555) is gone. The diff is now correctly scoped to the new schema-glob + pg_schema + publication-batching work layered on top of main's existing commit_ts_ms/before support. 👍

A few remaining items from the original pass, still present:

1. gofmt: the struct literal in input_pg_stream.go isn't gofmt-clean —

   DBSchemaPattern: schema,
   DBTables:        tables,

   gofmt -w wants DBSchemaPattern: schema, / DBTables: tables, to stay column-aligned with RefreshAuthToken: in the same literal. This will fail a gofmt -l/CI format check as-is.

2. validateSchemaPattern's quoted-identifier check (input_pg_stream.go) reimplements a shallow prefix/suffix/length check instead of delegating to sanitize.UnquotePostgresIdentifier, which this PR already uses in schema_resolver.go. The existing helper correctly handles escaped double-quotes ("foo""bar"); the new check doesn't.

3. No CHANGELOG.md entry — recent postgres_cdc PRs (#4554, #4555, ...) all added one under "Unreleased".

4. tests/current/ (Taskfile/docker-compose/setup.sql/test_config.yaml) reads like a personal manual-test harness — worth confirming this is meant to be committed long-term vs. a scratch dir that should be dropped or renamed to something more descriptive.

5. Worth a doc callout: schema-pattern resolution happens once at stream construction (resolveSchemas runs at startup only). For the stated multi-tenant use case, a new tenant_c schema created after the pipeline starts won't be picked up until restart. Not a bug, but non-obvious given the motivating use case.

6. Test coverage gap: no test for the "zero schemas matched" startup-error path (no schemas found matching pattern %q).

None of these block correctness — (1) is the only one that will mechanically fail CI as-is.