feat: Support for multiple OPDS servers (#1209)

* Add support for configuring and using multiple OPDS servers, replacing
the previous single-server limitation. Closes
https://github.com/crosspoint-reader/crosspoint-reader/issues/1178
* New OpdsServerStore singleton (modeled after WifiCredentialStore) that
persists up to 8 OPDS servers to /.crosspoint/opds.json with MAC-based
password obfuscation.
* One-time migration from legacy single-server fields in
CrossPointSettings to the new store on first boot.
* New OpdsServerListActivity for the device UI — works in two modes: a
settings list (add/edit/delete servers) and a picker (select which
server to browse). When only one server is configured, the picker is
skipped automatically.
* Renamed CalibreSettingsActivity → OpdsSettingsActivity for clarity. It
now edits individual OpdsServer entries (name, URL, username, password,
delete).
* OpdsBookBrowserActivity now receives an OpdsServer at construction and
uses its credentials for all fetches/downloads, and shows the server
name in the header.
* HttpDownloader::fetchUrl and downloadToFile accept optional per-call
username/password parameters instead of reading from global settings.
* REST API endpoints on CrossPointWebServer: GET /api/opds, POST
/api/opds, POST /api/opds/delete — passwords are never exposed over the
API (only a hasPassword flag), and omitting the password field on update
preserves the existing one.
* Web UI (SettingsPage.html) with dynamic OPDS server management cards —
add, edit, save, and delete servers from the browser.
<img width="932" height="906" alt="SCR-20260416-stvu"
src="https://github.com/user-attachments/assets/a8f18d84-4204-46a0-bb31-b73d24b3255f"
/>

* The OpdsServerStore JSON format and obfuscation scheme are identical
to WifiCredentialStore, so the same JsonSettingsIO infrastructure
handles both.
* The web API uses POST /api/opds/delete instead of DELETE /api/opds
because the ESP32 WebServer doesn't support the DELETE method with a
request body.
* Existing single-server configurations are migrated automatically — no
user action required. After migration the legacy CrossPointSettings
fields are cleared so it only runs once.
* The HttpDownloader changes are backward-compatible: the credential
parameters default to empty strings, so existing callers are unaffected.

---

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please be transparent about their usage as it
helps set the right context for reviewers.

Did you use AI tools to help write this code? _**< YES >**_

---------

Co-authored-by: Copilot <175728472+Copilot@users.noreply.github.com>

src/activities/browser/OpdsBookBrowserActivity.cpp

@@ -14,7 +14,6 @@
 #include <cstdio>
 #include <memory>
 
-#include "CrossPointSettings.h"
 #include "MappedInputManager.h"
 #include "OpdsFormatLabel.h"
 #include "activities/network/WifiSelectionActivity.h"
@@ -191,7 +190,9 @@ void OpdsBookBrowserActivity::render(RenderLock&&) {
   const Rect contentRect = UITheme::getContentRect(renderer, true, false);
   const int midY = contentRect.y + contentRect.height / 2;
 
-  renderer.drawCenteredText(UI_12_FONT_ID, 15, tr(STR_OPDS_BROWSER), true, EpdFontFamily::BOLD);
+  // Show server name in header if available, otherwise generic title
+  const char* headerTitle = server.name.empty() ? tr(STR_OPDS_BROWSER) : server.name.c_str();
+  renderer.drawCenteredText(UI_12_FONT_ID, 15, headerTitle, true, EpdFontFamily::BOLD);
 
   if (state == BrowserState::CHECK_WIFI) {
     renderer.drawCenteredText(UI_10_FONT_ID, midY, statusMessage.c_str());
@@ -303,21 +304,21 @@ void OpdsBookBrowserActivity::render(RenderLock&&) {
 }
 
 void OpdsBookBrowserActivity::fetchFeed(const std::string& path) {
-  if (strlen(SETTINGS.opdsServerUrl) == 0) {
+  if (server.url.empty()) {
     state = BrowserState::ERROR;
     errorMessage = tr(STR_NO_SERVER_URL);
     requestUpdate();
     return;
   }
 
-  std::string url = (path.rfind("http", 0) == 0) ? path : UrlUtils::buildUrl(SETTINGS.opdsServerUrl, path);
+  std::string url = (path.find("http") == 0) ? path : UrlUtils::buildUrl(server.url, path);
   LOG_DBG("OPDS", "Fetching: %s", url.c_str());
 
   OpdsParser parser;
 
   {
     OpdsParserStream stream{parser};
-    if (!HttpDownloader::fetchUrl(url, stream)) {
+    if (!HttpDownloader::fetchUrl(url, stream, server.username, server.password)) {
       state = BrowserState::ERROR;
       errorMessage = tr(STR_FETCH_FEED_FAILED);
       requestUpdate();
@@ -419,12 +420,14 @@ void OpdsBookBrowserActivity::downloadBook(const OpdsEntry& book, const OpdsAcqu
 
   LOG_DBG("OPDS", "Downloading: %s -> %s", downloadUrl.c_str(), filename.c_str());
 
-  const auto result =
-      HttpDownloader::downloadToFile(downloadUrl, filename, [this](const size_t downloaded, const size_t total) {
+  const auto result = HttpDownloader::downloadToFile(
+      downloadUrl, filename,
+      [this](const size_t downloaded, const size_t total) {
         downloadProgress = downloaded;
         downloadTotal = total;
         requestUpdate(true);
-      });
+      },
+      server.username, server.password);
 
   if (result == HttpDownloader::OK) {
     FsFile downloadedFile;
@@ -564,7 +567,6 @@ void OpdsBookBrowserActivity::checkAndConnectWifi() {
 }
 
 void OpdsBookBrowserActivity::launchWifiSelection() {
-  consumeBack = consumeConfirm = true;
   state = BrowserState::WIFI_SELECTION;
   requestUpdate();