Add connect to Wifi and File Manager Webserver (#41)

## Summary

- **What is the goal of this PR?**  
Implements wireless EPUB file management via a built-in web server,
enabling users to upload, browse, organize, and delete EPUB files from
any device on the same WiFi network without needing a computer cable
connection.

- **What changes are included?**
- **New Web Server**
([`CrossPointWebServer.cpp`](src/CrossPointWebServer.cpp),
[`CrossPointWebServer.h`](src/CrossPointWebServer.h)):
    - HTTP server on port 80 with a responsive HTML/CSS interface
    - Home page showing device status (version, IP, free memory)
    - File Manager with folder navigation and breadcrumb support
    - EPUB file upload with progress tracking
    - Folder creation and file/folder deletion
    - XSS protection via HTML escaping
- Hidden system folders (`.` prefixed, "System Volume Information",
"XTCache")
  
- **WiFi Screen** ([`WifiScreen.cpp`](src/screens/WifiScreen.cpp),
[`WifiScreen.h`](src/screens/WifiScreen.h)):
    - Network scanning with signal strength indicators
    - Visual indicators for encrypted (`*`) and saved (`+`) networks
- State machine managing: scanning, network selection, password entry,
connecting, save/forget prompts
    - 15-second connection timeout handling
    - Integration with web server (starts on connect, stops on exit)
  
- **WiFi Credential Storage**
([`WifiCredentialStore.cpp`](src/WifiCredentialStore.cpp),
[`WifiCredentialStore.h`](src/WifiCredentialStore.h)):
    - Persistent storage in `/sd/.crosspoint/wifi.bin`
- XOR obfuscation for stored passwords (basic protection against casual
reading)
    - Up to 8 saved networks with add/remove/update operations
  
- **On-Screen Keyboard**
([`OnScreenKeyboard.cpp`](src/screens/OnScreenKeyboard.cpp),
[`OnScreenKeyboard.h`](src/screens/OnScreenKeyboard.h)):
    - Reusable QWERTY keyboard component with shift support
    - Special keys: Shift, Space, Backspace, Done
    - Support for password masking mode
  
- **Settings Screen Integration**
([`SettingsScreen.h`](src/screens/SettingsScreen.h)):
    - Added WiFi action to navigate to the new WiFi screen
  
  - **Documentation** ([`docs/webserver.md`](docs/webserver.md)):
- Comprehensive user guide covering WiFi setup, web interface usage,
file management, troubleshooting, and security notes
    - See this for more screenshots!
- Working "displays the right way in GitHub" on my repo:
https://github.com/olearycrew/crosspoint-reader/blob/feature/connect-to-wifi/docs/webserver.md

**Video demo**


https://github.com/user-attachments/assets/283e32dc-2d9f-4ae2-848e-01f41166a731

## Additional Context

- **Security considerations**: The web server has no
authentication—anyone on the same WiFi network can access files. This is
documented as a limitation, recommending use only on trusted private
networks. Password obfuscation in the credential store is XOR-based, not
cryptographically secure.

- **Memory implications**: The web server and WiFi stack consume
significant memory. The implementation properly cleans up (stops server,
disconnects WiFi, sets `WIFI_OFF` mode) when exiting the WiFi screen to
free resources.

- **Async operations**: Network scanning and connection use async
patterns with FreeRTOS tasks to prevent blocking the UI. The display
task handles rendering on a dedicated thread with mutex protection.

- **Browser compatibility**: The web interface uses standard
HTML5/CSS3/JavaScript and is tested to work with all modern browsers on
desktop and mobile.

---------

Co-authored-by: Dave Allie <dave@daveallie.com>

src/activities/settings/SettingsActivity.cpp

@@ -8,9 +8,9 @@
 // Define the static settings list
 
 const SettingInfo SettingsActivity::settingsList[settingsCount] = {
-    {"White Sleep Screen", &CrossPointSettings::whiteSleepScreen},
-    {"Extra Paragraph Spacing", &CrossPointSettings::extraParagraphSpacing},
-    {"Short Power Button Click", &CrossPointSettings::shortPwrBtn}};
+    {"White Sleep Screen", SettingType::TOGGLE, &CrossPointSettings::whiteSleepScreen},
+    {"Extra Paragraph Spacing", SettingType::TOGGLE, &CrossPointSettings::extraParagraphSpacing},
+    {"Short Power Button Click", SettingType::TOGGLE, &CrossPointSettings::shortPwrBtn}};
 
 void SettingsActivity::taskTrampoline(void* param) {
   auto* self = static_cast<SettingsActivity*>(param);
@@ -65,9 +65,11 @@ void SettingsActivity::loop() {
     selectedSettingIndex = (selectedSettingIndex > 0) ? (selectedSettingIndex - 1) : (settingsCount - 1);
     updateRequired = true;
   } else if (inputManager.wasPressed(InputManager::BTN_DOWN) || inputManager.wasPressed(InputManager::BTN_RIGHT)) {
-    // Move selection down (with wrap-around)
-    selectedSettingIndex = (selectedSettingIndex < settingsCount - 1) ? (selectedSettingIndex + 1) : 0;
-    updateRequired = true;
+    // Move selection down
+    if (selectedSettingIndex < settingsCount - 1) {
+      selectedSettingIndex++;
+      updateRequired = true;
+    }
   }
 }
 
@@ -77,9 +79,16 @@ void SettingsActivity::toggleCurrentSetting() {
     return;
   }
 
+  const auto& setting = settingsList[selectedSettingIndex];
+
+  // Only toggle if it's a toggle type and has a value pointer
+  if (setting.type != SettingType::TOGGLE || setting.valuePtr == nullptr) {
+    return;
+  }
+
   // Toggle the boolean value using the member pointer
-  bool currentValue = SETTINGS.*(settingsList[selectedSettingIndex].valuePtr);
-  SETTINGS.*(settingsList[selectedSettingIndex].valuePtr) = !currentValue;
+  bool currentValue = SETTINGS.*(setting.valuePtr);
+  SETTINGS.*(setting.valuePtr) = !currentValue;
 
   // Save settings when they change
   SETTINGS.saveToFile();
@@ -106,8 +115,6 @@ void SettingsActivity::render() const {
   // Draw header
   renderer.drawCenteredText(READER_FONT_ID, 10, "Settings", true, BOLD);
 
-  // We always have at least one setting
-
   // Draw all settings
   for (int i = 0; i < settingsCount; i++) {
     const int settingY = 60 + i * 30;  // 30 pixels between settings
@@ -117,10 +124,14 @@ void SettingsActivity::render() const {
       renderer.drawText(UI_FONT_ID, 5, settingY, ">");
     }
 
-    // Draw setting name and value
+    // Draw setting name
     renderer.drawText(UI_FONT_ID, 20, settingY, settingsList[i].name);
-    bool value = SETTINGS.*(settingsList[i].valuePtr);
-    renderer.drawText(UI_FONT_ID, pageWidth - 80, settingY, value ? "ON" : "OFF");
+
+    // Draw value based on setting type
+    if (settingsList[i].type == SettingType::TOGGLE && settingsList[i].valuePtr != nullptr) {
+      bool value = SETTINGS.*(settingsList[i].valuePtr);
+      renderer.drawText(UI_FONT_ID, pageWidth - 80, settingY, value ? "ON" : "OFF");
+    }
   }
 
   // Draw help text

src/activities/settings/SettingsActivity.h

@@ -4,6 +4,7 @@
 #include <freertos/task.h>
 
 #include <cstdint>
+#include <functional>
 #include <string>
 #include <vector>
 
@@ -11,10 +12,13 @@
 
 class CrossPointSettings;
 
+enum class SettingType { TOGGLE };
+
 // Structure to hold setting information
 struct SettingInfo {
   const char* name;                        // Display name of the setting
-  uint8_t CrossPointSettings::* valuePtr;  // Pointer to member in CrossPointSettings
+  SettingType type;                        // Type of setting
+  uint8_t CrossPointSettings::* valuePtr;  // Pointer to member in CrossPointSettings (for TOGGLE)
 };
 
 class SettingsActivity final : public Activity {