Replace Andmore ID SSO with local login

fitme3070.pt delegated all authentication to hub.andmore.pt: views/auth/*
were bounce stubs, and because this domain is outside the .andmore.pt cookie
scope the real handoff was a one-time HTTPS ticket redeem. Bring identity back
in-house — passwords live in users.password_hash, which the SSO migration
never dropped.

Removed: config/sso.php, IDENTITY_MODE, every SSO_* constant and env key,
identity_is_federated() and the cookie/ticket paths in the auth views and the
public-site bootstrap. ANDMORE_ID_URL stays — it is still the hub /notify
endpoint for outbound email/SMS, which the reset mails ride on, and has
nothing to do with authentication now.

Added, ported from the fotografia.andmore.pt sibling rather than invented:

  - auth_login() with transparent password_needs_rehash upgrades and the
    last_login trail; auth_register_client(); auth_set_password(); the
    single-use 2h reset tokens.
  - Real login / register / forgot_password / reset_password pages on a new
    anonymous shell (includes/auth_header.php). includes/header.php renders
    the backoffice sidebar and a logout button, which is wrong for a visitor
    who is not signed in yet.
  - safe_return_path(), so a crafted ?return_to= cannot bounce a freshly
    authenticated user off-site.
  - Per-IP throttling on login, register and reset-request. Successes count
    too, so a guessed password cannot be parlayed into stuffing the rest of
    the user list from the same IP.
  - views/user/set_password.php: admin override for anyone whose email is
    undeliverable. Prefers mailing an invite link so the backoffice never
    handles the password. A plain admin cannot act on a sysadmin, and nobody
    can use it on themselves — self-service goes through profile.php, which
    demands the current password so a hijacked session cannot lock the owner
    out.

Accounts provisioned during the SSO era have password_hash NULL. They get in
via the reset email, or by registering again with the same address:
auth_register_client() claims a passwordless row, but only a plain `client`
one, so knowing a staff address does not let anyone self-assign the role.

users.andmore_id is deliberately left in place. No code reads it any more, but
it records which central identity each row was linked to.

Deployment: apply database/migration_20260913_local_auth.sql (password_resets
+ auth_attempts) in the SAME sysadmin session that pulls this commit — the
forgot-password flow needs that table, and after the pull a login requires a
local password.

Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>

database/migration_20260913_local_auth.sql

@@ -0,0 +1,34 @@
+-- Local authentication: password reset tokens + per-IP attempt throttling.
+--
+-- Added when fitme3070 stopped delegating login to the Andmore ID hub and went
+-- back to owning its own passwords (users.password_hash, which was never
+-- dropped). See config/functions_user.php and config/functions_throttle.php.
+--
+-- Safe to re-run: every statement is IF NOT EXISTS.
+
+CREATE TABLE IF NOT EXISTS `password_resets` (
+  `id`         INT UNSIGNED NOT NULL AUTO_INCREMENT,
+  `user_id`    INT UNSIGNED NOT NULL,
+  `token`      VARCHAR(64) NOT NULL,
+  `expires_at` DATETIME NOT NULL,
+  `used_at`    DATETIME DEFAULT NULL,
+  `created_at` DATETIME NOT NULL DEFAULT CURRENT_TIMESTAMP,
+  PRIMARY KEY (`id`),
+  UNIQUE KEY `uq_pr_token` (`token`),
+  KEY `idx_pr_user` (`user_id`),
+  CONSTRAINT `fk_pr_user` FOREIGN KEY (`user_id`) REFERENCES `users` (`id`) ON DELETE CASCADE
+) ENGINE=InnoDB DEFAULT CHARSET=utf8mb4 COLLATE=utf8mb4_unicode_ci;
+
+CREATE TABLE IF NOT EXISTS `auth_attempts` (
+  `id`           BIGINT UNSIGNED NOT NULL AUTO_INCREMENT,
+  `ip`           VARCHAR(45) NOT NULL,
+  `scope`        VARCHAR(20) NOT NULL,
+  `attempted_at` DATETIME NOT NULL DEFAULT CURRENT_TIMESTAMP,
+  PRIMARY KEY (`id`),
+  KEY `idx_aa_window` (`ip`, `scope`, `attempted_at`)
+) ENGINE=InnoDB DEFAULT CHARSET=utf8mb4 COLLATE=utf8mb4_unicode_ci;
+
+-- `users.andmore_id` is intentionally NOT dropped. It no longer has any code
+-- reading or writing it, but it records which central Andmore ID each row was
+-- linked to during the SSO era — useful if those accounts ever need to be
+-- reconciled. Drop it by hand once that history stops mattering.