feat: P2 RBAC defers — REST API + invitation workflow

Closes the P2 items from /tmp/service/new/01-TZ-rbac §4.1 §4.2.

== User invitation workflow ==

New columns on users: invited_at, invited_by_id (FK self), accepted_at,
invitation_token (sha256 hash, indexed). Migration is idempotent.

User::sendInvitation($invitedBy = auth()->user())
  - generates 64-char random token
  - stores sha256(token) in invitation_token column (never plaintext)
  - marks invited_at = now(), status = inactive
  - queues UserInvitationMail to the user's email with the signed accept URL
  - returns the raw token (for tests / API consumers)

User::findByInvitationToken($rawToken) hashes + lookups.
User::acceptInvitation($password) sets password (hashed cast), clears
invitation_token, marks accepted_at + email_verified_at, status = active.

Web routes (no auth — token IS the credential):
  GET  /invitations/{token}  → password-set form
  POST /invitations/{token}  → validates min:8 + confirmed, accepts

Tokens expire after 7 days (checked against invited_at). Expired and
invalid tokens render dedicated views (invitations/expired.blade.php,
invitations/invalid.blade.php) instead of generic 404 — so the user
knows to ask for a resend.

UserInvitationMail uses Filament's existing markdown layout; subject
includes the tenant display_name.

== REST API ==

Twenty new endpoints under /api/v1/ (Sanctum auth + tenant scoping
via the existing EnsureTokenMatchesTenant middleware). All gated by
ADMIN_USERS_* / ADMIN_ROLES_MANAGE permissions; mechanic-level token
gets 403.

Users:
  GET    /users                                  — paginated + role/status/q filters
  GET    /users/{u}                              — eager-loads roles + overrides + invitedBy
  POST   /users                                  — creates inactive user + sends invitation
  PATCH  /users/{u}                              — update name/email/role/status
  DELETE /users/{u}                              — soft delete
  POST   /users/{u}/activate
  POST   /users/{u}/deactivate                   — also revokes all sessions
  POST   /users/{u}/resend-invitation
  POST   /users/{u}/force-password-reset         — re-sends invitation
  GET    /users/{u}/sessions                     — list active sessions (from sessions table)
  DELETE /users/{u}/sessions                     — revoke all
  DELETE /users/{u}/sessions/{sessionId}         — revoke one
  GET    /users/{u}/roles                        — assigned roles
  POST   /users/{u}/roles                        — assign role
  DELETE /users/{u}/roles/{role}                 — remove role
  GET    /users/{u}/permissions                  — effective: role perms + grants - active denies
  POST   /users/{u}/permission-overrides         — add grant/deny (with optional expires_at)
  DELETE /users/{u}/permission-overrides/{perm}

Roles:
  apiResource roles                              — index/show/store/update/destroy
                                                   (system roles guarded against rename/delete)
  GET    /roles/{r}/permissions
  PUT    /roles/{r}/permissions                  — bulk sync
  GET    /permissions                            — catalog: flat list + grouped + labels + role labels

Authorization is uniform: every controller method calls $this->authorize()
which throws 403 if canDo(perm) is false. canDo() already honors the
overrides + admin bypass + audit log from earlier commits, so the API
behaves identically to the Filament UI.

== Tests ==

InvitationFlowTest (8): token generation + sha256 storage + queued mail,
findByInvitationToken happy/sad path, accept sets password + activates,
GET form renders, POST accepts + redirects, invalid token view,
backdated invited_at → expired view, password too short → validation error.

RbacApiTest (12): admin can list users, mechanic 403, create user
queues invitation, assign+remove role round-trip, effective permissions
endpoint subtracts active denies, add+remove override via API,
role index returns 7 system roles with permission counts (51 for owner),
role sync permissions, system role destroy rejected with 422,
permission catalog endpoint returns all 51 + grouped + labels,
revoke all sessions deletes only target user's rows.

Suite: 234 passed (659 assertions). Was 214.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

resources/views/invitations/expired.blade.php

@@ -0,0 +1,4 @@
+<!DOCTYPE html>
+<html lang="ro"><head><meta charset="UTF-8"><title>Invitație expirată</title>
+<style>body{font-family:-apple-system,sans-serif;background:#f5f7fa;display:flex;align-items:center;justify-content:center;min-height:100vh;margin:0;color:#1a202c}.card{background:white;padding:32px;border-radius:12px;box-shadow:0 4px 20px rgba(0,0,0,0.08);max-width:420px;text-align:center}</style></head>
+<body><div class="card"><h1>Invitație expirată</h1><p style="color:#4a5568">Linkul de invitație a expirat (durata maximă: 7 zile). Roagă administratorul să retrimită invitația.</p></div></body></html>