fix: před stahováním ověřit přihlášení přes islogged (#72) (#80)

* fix: před stahováním ověřit přihlášení přes islogged

Server při vypršelé session nevrací chybu, ale tiše odpoví jako
anonymnímu uživateli (jen přístupnost A). Plugin proto před stahováním
volá /api/user/islogged; při 'nologged' se jednou znovu přihlásí
z uložených údajů, a když to nejde, varuje v liště, že stahuje anonymně.

- amcr_tools: _check_islogged, _ensure_logged_in, volání v load_amcr_data
- smoke test: 7 offline scénářů stavu přihlášení
- README; changelog v2.2.0 v metadata.txt
- openspec/changes/fix-session-expiry-islogged: návrh, spec, design, úkoly

Closes #72. Připraveno s pomocí AI (Claude), ručně zkontrolováno.

* feat: odebrání přihlašovacích údajů uživatele i odhlásí

Dosud zůstala přihlášená session v paměti až do restartu QGIS, takže
se po „Odebrat uložené přihlašovací údaje“ dál stahovalo jako přihlášený.
Nově se session odhlásí na serveru (GET /api/user/logout) a zahodí;
když server neodpoví, zahodí se aspoň lokálně.

- amcr_tools: logout_from_api; amcr_dialog: volání v _forget_credentials
- smoke test: odhlášení, chyba sítě, bez session
- README, changelog v2.2.0, OpenSpec (požadavek + úkoly 2b; 3.3 ověřeno)

Připraveno s pomocí AI (Claude), ručně zkontrolováno.

* chore: archivovat OpenSpec změnu fix-session-expiry-islogged

Všechny úkoly hotové (2b.2 – odhlášení – ověřeno ručně v QGIS),
archivováno s --skip-specs (stupeň change-tracked, bez openspec/specs/).

Připraveno s pomocí AI (Claude), ručně zkontrolováno.

openspec/changes/archive/2026-10-02-fix-session-expiry-islogged/specs/amcr-session/spec.md

@@ -0,0 +1,70 @@
+# Spec Delta
+
+## Purpose
+
+Keeps a logged-in user's data downloads from digiarchiv running under a valid
+login, and makes it visible when a download falls back to anonymous access.
+
+## ADDED Requirements
+
+### Requirement: Login state is verified before a download
+Before starting a data download, the plugin SHALL ask the server whether the
+current session is logged in, whenever an in-memory session exists or login
+credentials are stored. Users with neither SHALL download anonymously without
+this check.
+
+#### Scenario: Valid session
+- **WHEN** a session exists and the server reports it as logged in
+- **THEN** the download proceeds with that session and no re-login happens
+
+#### Scenario: Anonymous user without stored credentials
+- **WHEN** no session exists and no credentials are stored
+- **THEN** no login-state request is sent and the download proceeds anonymously without a warning
+
+### Requirement: Expired login is renewed transparently
+When the server reports the session as not logged in and credentials are
+stored, the plugin SHALL log in again and run the whole download with the new
+session.
+
+#### Scenario: Session expired after inactivity
+- **WHEN** the user downloads data more than one hour after the previous download within the same QGIS run
+- **THEN** the plugin logs in again with the stored credentials and the download returns the same records as for a fresh login
+
+#### Scenario: No session yet, credentials stored
+- **WHEN** the first download after QGIS start is requested and credentials are stored
+- **THEN** the plugin logs in and verifies that the new session is logged in before downloading
+
+### Requirement: Anonymous fallback is reported to the user
+When the plugin expected to be logged in but cannot obtain a logged-in
+session, it SHALL show a warning in the QGIS message bar stating that the
+download runs anonymously and contains only records with access level A.
+
+#### Scenario: Re-login fails
+- **WHEN** the session has expired and logging in again with stored credentials fails
+- **THEN** a warning appears in the message bar and the download continues anonymously
+
+#### Scenario: Session expired and credentials removed
+- **WHEN** an in-memory session has expired and no credentials are stored any more
+- **THEN** a warning appears in the message bar and the download continues anonymously
+
+### Requirement: Failed state check does not block the download
+If the login-state check cannot be completed (network error or a response
+that is not valid JSON), the plugin SHALL log a warning and proceed with the
+download using the current session.
+
+#### Scenario: Login-state endpoint unreachable
+- **WHEN** the login-state request fails with a network error
+- **THEN** a warning is written to the log and the download is attempted as usual
+
+### Requirement: Removing stored credentials logs the user out
+When the user removes the stored credentials, the plugin SHALL log the
+current session out on the server and discard it, so that later downloads
+run anonymously without restarting QGIS.
+
+#### Scenario: Credentials removed while logged in
+- **WHEN** the user removes the stored credentials while a logged-in session exists
+- **THEN** the session is logged out on the server and the next download is anonymous without a warning
+
+#### Scenario: Server unreachable during logout
+- **WHEN** the logout request fails with a network error
+- **THEN** the session is still discarded locally and the user is told the next download will be anonymous