Rebuild API Server on the PilotVault structure

Mirror PilotVault's API Server layout and add the superadmin console,
plugin system, runtime PocketBase settings, and user/organization
management. The car domain (cars, service records, parts, sharing) is
carried over unchanged apart from the auth switch.

Layout: main.go -> cmd/server/main.go; module carcontrol/api ->
drivervault/apiserver. internal/api is split by concern (auth, users,
orgs, settings, plugins, status, health, respond).

Auth: replace the server-minted HS256 JWT and the sessions collection
with a PocketBase token proxy. /api/auth/login relays PocketBase's
{token, record}, and every protected request re-resolves that token
against PocketBase, so a role change or deletion takes effect at once
instead of waiting out a token. AUTH_SECRET is obsolete and internal/auth
is gone. Per-device session listing/revocation goes with it: PocketBase
tokens are stateless. Changing a password rotates the user's token key,
which invalidates every token already issued.

Roles: add superadmin alongside user/admin, plus an organizations
collection and users.organization. Admins are scoped to their own
organization; superadmins span all of them. Guards prevent changing your
own role, deleting your own account, an admin touching a superadmin, and
deleting an organization that still has members.

Plugins: new internal/plugins package with one contract over two kinds --
builtin (compiled in) and external (any HTTP service, registered at
runtime with no rebuild). State persists to plugins.json; secrets are
masked on read and preserved when saved back at the mask.

PocketBase settings: /api/admin/pb-config applies a new connection at
runtime and persists it to .env. It deliberately does not require a
working service account, so a wrong or unreachable connection can still
be fixed from the panel.

Panel: rebuilt as the superadmin console -- login gate, status, users,
organizations, PocketBase, plugins, and the endpoint reference.

Clients: update the Web App and Phone App for the PocketBase token shape,
the move of user management to /api/users ({users}/{user} envelopes, with
password resets folded into PATCH), and the removal of sessions. Both now
mirror the server's real guards rather than the old last-admin rule, and
parse PocketBase's field-level error shape.

Config: modern POCKETBASE_*/API_ADDR names with legacy PB_*/PORT
fallbacks, so existing .env files keep working. Also fixes /api/status
probing the Web App on 8090 instead of DriverVault's 5173.

Run scripts/setup-pocketbase.mjs to add the organizations collection and
grow users.role; every client must log in once more.

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

API Server/internal/plugins/doc.go

@@ -0,0 +1,20 @@
+package plugins
+
+// Deferred extension points (deliberately NOT in v1 — the "Management MVP").
+// The contract and manager are shaped so these can be added without a redesign:
+//
+//   - Invocation API: the Plugin.Invoke method already exists; a
+//     POST /api/admin/plugins/{name}/action endpoint + a normalized request/
+//     response envelope would expose it. Add a mapper layer so core logic never
+//     depends on a provider's schema.
+//   - Resilience: wrap plugin calls with retry/backoff + a circuit breaker, and
+//     record per-plugin latency/error/quota metrics for the panel.
+//   - Per-tenant credentials: today config is a single global blob per plugin.
+//     A (pluginName, orgID/userID) → config store would let users connect their
+//     own third-party accounts.
+//   - Audit logging: record which plugin accessed what and when.
+//   - Sandboxing: the "external" plugin kind is the isolation story — run less
+//     trusted plugins as separate processes/containers behind the HTTP contract.
+//   - Hot-adding builtin Go code without a rebuild is intentionally unsupported
+//     (Go .so plugins are Linux-only and toolchain-fragile); use the external
+//     HTTP kind to add plugins at runtime instead.