Add secrets infrastructure: DB tables, shared types, env binding model, and migration improvements

Introduce company_secrets and company_secret_versions tables for
encrypted secret storage. Add EnvBinding discriminated union (plain vs
secret_ref) to replace raw string env values in adapter configs. Add
hiddenAt column to issues for soft-hiding. Improve migration system
with journal-ordered application and manual fallback when Drizzle
migrator can't reconcile history.

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

packages/shared/src/api.ts

@@ -8,6 +8,7 @@ export const API = {
   issues: `${API_PREFIX}/issues`,
   goals: `${API_PREFIX}/goals`,
   approvals: `${API_PREFIX}/approvals`,
+  secrets: `${API_PREFIX}/secrets`,
   costs: `${API_PREFIX}/costs`,
   activity: `${API_PREFIX}/activity`,
   dashboard: `${API_PREFIX}/dashboard`,