Feat v0.5.5 upgrade testing

Upgrade test harness, schema edge case tests, and two bug fixes found
during testing.

New: docker-compose-upgrade.yml + ci/e2e-upgrade-test.sh for single-replica
upgrade testing (seed → upgrade → verify). ci/e2e-upgrade-rolling.sh for
multi-replica rolling upgrade with shared Postgres. 11 Go unit tests for
schema migration edge cases, settings preservation, and package compat.

Fix: Bundled permission auto-grant on Postgres — SQL used SQLite-style
`granted = 1` on BOOLEAN columns. Now dialect-aware (true/false on PG).
Fix: E2E chat test API fields — login, token extraction, profile endpoint.

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

CHANGELOG.md

@@ -2,6 +2,38 @@
 
 All notable changes to Switchboard Core are documented here.
 
+## v0.5.5 — Upgrade Testing
+
+### Fixed
+
+- **Bundled permission auto-grant on Postgres**: The `InstallBundledPackages`
+  auto-grant SQL used SQLite-style `granted = 1` / `granted = 0` which fails
+  on Postgres BOOLEAN columns. Now dialect-aware: `true`/`false` on Postgres,
+  `1`/`0` on SQLite. This caused bundled extensions (notes, chat-core, etc.)
+  to install with permissions not granted on Postgres deployments.
+- **E2E test API field corrections**: Fixed `ci/e2e-chat-test.sh` login field
+  (`"username"` → `"login"`), token extraction (`"token"` → `"access_token"`),
+  and profile endpoint (`/api/v1/me` → `/api/v1/profile`).
+
+### Added
+
+- **Upgrade test harness**: `docker-compose-upgrade.yml` + `ci/e2e-upgrade-test.sh`
+  orchestrate a full upgrade cycle: build old image, seed data (notes,
+  conversations, messages, settings), stop old, start new, verify data integrity
+  post-upgrade. Covers auth, notes, conversations, packages, and settings.
+- **Rolling upgrade test**: `ci/e2e-upgrade-rolling.sh` tests rolling upgrade
+  with 2 replicas sharing Postgres. Upgrades one replica at a time, verifies
+  cross-replica reads during the mixed-version window.
+- **11 new Go tests** in `upgrade_test.go`:
+  - Schema edge cases: add index (idempotent), add column (idempotent),
+    multi-column add, row preservation across migration.
+  - Settings migration: global/team/user overrides preserved across package
+    update, new keys get defaults, removed keys not deleted.
+  - Package compatibility: bundled skip-if-present on restart, dormant status
+    for unmet requires, enabled/type preserved across version bump.
+  - Direct `MigrateExtTables` tests: new table creation, column add with row
+    preservation, index idempotency.
+
 ## v0.5.4 — Package Updates
 
 ### Added