fix(backend): guard startMcp and use direct url in mastra store

[JOY (JOY)]

What kind of change does this PR introduce?

Bug fix & Stability

Why was this change needed?

1. Ensures startMcp does not block app.listen(port) during backend boot if Mastra's internal table migrations encounter connection limits.
2. Directs Mastra PostgresStore to use DATABASE_DIRECT_URL (direct PostgreSQL connection) instead of pooler session mode.

Checklist:

• I have read the CONTRIBUTING guide.
• I have signed the Contributor License Agreement (CLA).
• I checked that there were no similar issues or PRs already open for this.
• This PR fixes just ONE issue

---

Note

Medium Risk
Failed MCP init is swallowed so Copilot/MCP may be unavailable without a hard crash; switching Mastra to a direct DB URL changes connection behavior and must match deployment env vars.

Overview
Backend boot no longer fails when Mastra MCP initialization errors (e.g. Postgres migration/connection limits during startup). startMcp is wrapped in try/catch so failures are logged and the API can still reach app.listen.

Mastra PostgresStore now prefers DATABASE_DIRECT_URL over DATABASE_URL, so Mastra uses a direct Postgres connection instead of a pooler session URL when both are set.

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[gemini-code-assist]

Code Review

This pull request wraps the Mastra MCP server initialization in a try-catch block to handle startup failures gracefully, and updates the Mastra PostgresStore connection string to fall back to DATABASE_URL if DATABASE_DIRECT_URL is not set. The review feedback recommends adding explicit validation for these environment variables to avoid runtime crashes caused by unsafe non-null assertions.

[gemini-code-assist]

Using the non-null assertion operator ! on process.env.DATABASE_URL is unsafe because if both DATABASE_DIRECT_URL and DATABASE_URL are missing, it will pass undefined to PostgresStore, leading to a runtime crash with a cryptic error. It is safer to validate that at least one of these environment variables is defined and throw a clear configuration error if they are missing.

  connectionString: (() => {
    const url = process.env.DATABASE_DIRECT_URL || process.env.DATABASE_URL;
    if (!url) {
      throw new Error('Database connection URL is missing. Please set DATABASE_DIRECT_URL or DATABASE_URL.');
    }
    return url;
  })(),