My Library: Tab bar w/ Recent Books + File Browser (#250)

# Summary

This PR introduces a reusable Tab Bar component and combines the Recent
Books and File Browser into a unified tabbed page called "My Library"
accessible from the Home screen.

## Features
### New Tab Bar Component
A flexible, reusable tab bar component added to `ScreenComponents` that
can be used throughout the application.

### New Scroll Indicator Component
A page position indicator for lists that span multiple pages.
**Features:**
- Up/down arrow indicators
- Current page fraction display (e.g., "1/3")
- Only renders when content spans multiple pages

### My Library Activity
A new unified view combining Recent Books and File Browser into a single
tabbed page.

**Tabs:**
- **Recent** - Shows recently opened books
- **Files** - Browse SD card directory structure

**Navigation:**
- Up/Down or Left/Right: Navigate through list items
- Left/Right (when first item selected): Switch between tabs
- Confirm: Open selected book or enter directory
- Back: Go up directory (Files tab) or return home
- Long press Back: Jump to root directory (Files tab)

**UI Elements:**
- Tab bar with selection indicator
- Scroll/page indicator on right side
- Side button hints (up/down arrows)
- Dynamic bottom button labels ("BACK" in subdirectories, "HOME" at
root)

## Tab Bar Usage
The tab bar component is designed to be reusable across different
activities. Here's how to use it:

### Basic Example
```cpp
#include "ScreenComponents.h"
void MyActivity::render() const {
  renderer.clearScreen();
  
  // Define tabs with labels and selection state
  std::vector<TabInfo> tabs = {
    {"Tab One", currentTab == 0},   // Selected when currentTab is 0
    {"Tab Two", currentTab == 1},   // Selected when currentTab is 1
    {"Tab Three", currentTab == 2}  // Selected when currentTab is 2
  };
  
  // Draw tab bar at Y position 15, returns height of the tab bar
  int tabBarHeight = ScreenComponents::drawTabBar(renderer, 15, tabs);
  
  // Position your content below the tab bar
  int contentStartY = 15 + tabBarHeight + 10; // Add some padding
  
  // Draw content based on selected tab
  if (currentTab == 0) {
    renderTabOneContent(contentStartY);
  } else if (currentTab == 1) {
    renderTabTwoContent(contentStartY);
  } else {
    renderTabThreeContent(contentStartY);
  }
  
  renderer.displayBuffer();
}
```
Video Demo: https://share.cleanshot.com/P6NBncFS

<img width="250"
src="https://github.com/user-attachments/assets/07de4418-968e-4a88-9b42-ac5f53d8a832"
/>
<img width="250"
src="https://github.com/user-attachments/assets/e40201ed-dcc8-4568-b008-cd2bf13ebb2a"
/>
<img width="250"
src="https://github.com/user-attachments/assets/73db269f-e629-4696-b8ca-0b8443451a05"
/>

---------

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

src/activities/home/HomeActivity.cpp

@@ -23,7 +23,7 @@ void HomeActivity::taskTrampoline(void* param) {
 }
 
 int HomeActivity::getMenuItemCount() const {
-  int count = 3;  // Browse files, File transfer, Settings
+  int count = 3;  // My Library, File transfer, Settings
   if (hasContinueReading) count++;
   if (hasOpdsUrl) count++;
   return count;
@@ -169,15 +169,15 @@ void HomeActivity::loop() {
     // Calculate dynamic indices based on which options are available
     int idx = 0;
     const int continueIdx = hasContinueReading ? idx++ : -1;
-    const int browseFilesIdx = idx++;
+    const int myLibraryIdx = idx++;
     const int opdsLibraryIdx = hasOpdsUrl ? idx++ : -1;
     const int fileTransferIdx = idx++;
     const int settingsIdx = idx;
 
     if (selectorIndex == continueIdx) {
       onContinueReading();
-    } else if (selectorIndex == browseFilesIdx) {
-      onReaderOpen();
+    } else if (selectorIndex == myLibraryIdx) {
+      onMyLibraryOpen();
     } else if (selectorIndex == opdsLibraryIdx) {
       onOpdsBrowserOpen();
     } else if (selectorIndex == fileTransferIdx) {
@@ -500,9 +500,9 @@ void HomeActivity::render() {
 
   // --- Bottom menu tiles ---
   // Build menu items dynamically
-  std::vector<const char*> menuItems = {"Browse Files", "File Transfer", "Settings"};
+  std::vector<const char*> menuItems = {"My Library", "File Transfer", "Settings"};
   if (hasOpdsUrl) {
-    // Insert Calibre Library after Browse Files
+    // Insert Calibre Library after My Library
     menuItems.insert(menuItems.begin() + 1, "Calibre Library");
   }
 
@@ -541,7 +541,7 @@ void HomeActivity::render() {
     renderer.drawText(UI_10_FONT_ID, textX, textY, label, !selected);
   }
 
-  const auto labels = mappedInput.mapLabels("", "Confirm", "Up", "Down");
+  const auto labels = mappedInput.mapLabels("", "Select", "Up", "Down");
   renderer.drawButtonHints(UI_10_FONT_ID, labels.btn1, labels.btn2, labels.btn3, labels.btn4);
 
   const bool showBatteryPercentage =