feat: configure explicit Postgres connection pool and timeouts

[rubenhensen]

Closes #100.

Gives the app's Postgres client explicit, env-tunable pool sizing and timeouts. Previously src/lib/server/db/index.ts used postgres(env.DATABASE_URL) with library defaults (notably no connect/idle timeouts), and the pool couldn't be sized against Postgres max_connections across replicas.

Changes

• db/index.ts now sets max, idle_timeout, connect_timeout, and max_lifetime, each overridable via env (DB_POOL_MAX, DB_IDLE_TIMEOUT, DB_CONNECT_TIMEOUT, DB_MAX_LIFETIME) with sensible defaults.
• .env.example documents the new optional knobs.

Already covered

The other half of #100 — the migration script using a single short-lived connection — was already in place: scripts/migrate.ts uses postgres(DATABASE_URL, { max: 1 }) and calls client.end(). No change needed there.

[dobby-coder]

On it, @rubenhensen! I'm reviewing PR #114 (Postgres pool sizing and timeouts) for correctness and rule-compliance now — I'll post a consolidated review shortly.

[dobby-coder]

Approve — clean, well-scoped change.

Review: intFromEnv correctly falls back on unset/empty/non-numeric/zero/negative/float input; the four postgres.js options (max, idle_timeout, connect_timeout, max_lifetime) are valid for postgres@3.4.x, and the .env.example defaults match the code (10 / 20 / 10 / 1800). Build (vite) OK and all 83 unit tests pass.

Rule compliance: conventional-commit title (feat:), non-draft, Closes #100 present, PR body matches the delivered diff. No violations found across the rule set.

Nit (non-blocking): a small unit test pinning intFromEnv's fallback branches would lock in the behaviour that was verified manually here — worth adding if you touch this again.

[dobby-coder]

Reviewed and approved! Everything looks solid — conventional title, closes #100, intFromEnv fallbacks are correct, postgres.js option names check out for 3.4.x, and the .env.example defaults match the code. All 83 unit tests pass.

One non-blocking nit in the review: it'd be nice to have a unit test covering the fallback branches of intFromEnv, but that's not a blocker.

Review: approved

[rubenhensen]

Thanks @dobby-coder — added tests/unit/db-pool.test.ts covering intFromEnv's branches (valid int, unset, empty, non-numeric, zero/negative, float fallback). intFromEnv is now exported; the test stubs postgres/drizzle/$env so importing the db module doesn't open a connection. 6/6 pass locally.