feat: wire enable_realtime into DATABASE_SETTINGS_SQL COALESCE cascade

[pyramation]

Summary

Removes the hardcoded enableRealtime: false placeholder and wires enable_realtime into the DATABASE_SETTINGS_SQL COALESCE cascade, following the same pattern as all other feature flags (enable_llm, enable_ltree, etc.).

This is a follow-up to constructive-db#1105 (which added the enable_realtime column to database_settings and api_settings) and #1119 (which integrated RealtimeManager into the preset but hardcoded the flag to false because the column didn't exist yet).

Three changes in api.ts:

1. SQL: added COALESCE(aps.enable_realtime, ds.enable_realtime) AS resolved_enable_realtime to the query
2. Type: added resolved_enable_realtime: boolean to DatabaseSettingsRow
3. Mapping: replaced enableRealtime: false with enableRealtime: row.resolved_enable_realtime in toDatabaseSettings

Updates since last revision

Added enable_realtime column to the integration test seed DDL (simple-seed-services/setup.sql). Without this, the DATABASE_SETTINGS_SQL query fails against the test database (column doesn't exist), queryDatabaseSettings catches the error and returns undefined, and all feature flags fall back to defaults — causing the Bob restricted API: uploadAppFile NOT exposed test to fail because the api_settings override for enable_presigned_uploads was silently ignored.

Review & Testing Checklist for Human

• Deployment ordering: This PR assumes enable_realtime already exists in both services_public.database_settings and services_public.api_settings. If constructive-db#1105 has not been deployed to an environment, the DATABASE_SETTINGS_SQL query will fail. The failure is caught by queryDatabaseSettings's try/catch (returns undefined + logs a warning), but this means all database settings become undefined for that tenant — not just realtime. Verify feat: add DataBillingMeter and DataAggregateLimitCounter node types #1105 is deployed before rolling this out.
• Verify the COALESCE cascade resolves correctly: api_settings.enable_realtime is nullable (NULL inherits from database_settings), while database_settings.enable_realtime is NOT NULL DEFAULT false. Confirm COALESCE produces the right result: api-level override wins when non-null, otherwise falls back to database-level default.
• Test seed DDL stays in sync: The test seed in simple-seed-services/setup.sql manually mirrors the production database_settings / api_settings schema. Any future column additions to these tables will need a corresponding update to the seed DDL, or the same silent-failure pattern will recur.

Notes

• With this merged, setting enable_realtime = true in database_settings (or per-API in api_settings) will cause RealtimeManager to start and the RealtimeSubscriptionsPreset to be included for that tenant.
• The next step toward integration testing is deploying realtime_module to a test database and applying DataRealtime to a table (which automatically adds the @realtime smart tag).

Link to Devin session: https://app.devin.ai/sessions/19485cf5cc58416a9f86068563d512f5
Requested by: @pyramation

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