Make Oban table creation configurable to use custom schema (avoid public schema pollution)

[ElemTran]

Problem

PR #3167 introduced Oban into Logflare (merged on 2026-03-02), and currently Oban creates its tables in the public database schema by default. This causes unnecessary schema pollution of the public namespace, which is undesirable for database organization and isolation of Logflare's analytics-related tables.

Expected Solution

Allow configuring the database schema for Oban tables via environment variables and/or direct config, with the intended target schema being _analytics for Logflare's analytics workloads.

1. Set the Oban prefix to _analytics by default for Logflare: config :logflare, Oban, prefix: "_analytics"
2. Add environment variable support for flexible schema control:
   • Primary: LOGFLARE_OBAN_SCHEMA (takes precedence if set)
   • Fallback: Reuse existing DB_SCHEMA if LOGFLARE_OBAN_SCHEMA is not provided

Thank you for considering this configuration improvement!

[Ziinc]

thanks for raising this issue, definitely an undesirable behaviour.