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/reader/ReaderActivity.cpp

@@ -2,7 +2,6 @@
 
 #include "Epub.h"
 #include "EpubReaderActivity.h"
-#include "FileSelectionActivity.h"
 #include "Txt.h"
 #include "TxtReaderActivity.h"
 #include "Xtc.h"
@@ -73,56 +72,10 @@ std::unique_ptr<Txt> ReaderActivity::loadTxt(const std::string& path) {
   return nullptr;
 }
 
-void ReaderActivity::onSelectBookFile(const std::string& path) {
-  currentBookPath = path;  // Track current book path
-  exitActivity();
-  enterNewActivity(new FullScreenMessageActivity(renderer, mappedInput, "Loading..."));
-
-  if (isXtcFile(path)) {
-    // Load XTC file
-    auto xtc = loadXtc(path);
-    if (xtc) {
-      onGoToXtcReader(std::move(xtc));
-    } else {
-      exitActivity();
-      enterNewActivity(new FullScreenMessageActivity(renderer, mappedInput, "Failed to load XTC",
-                                                     EpdFontFamily::REGULAR, EInkDisplay::HALF_REFRESH));
-      delay(2000);
-      onGoToFileSelection();
-    }
-  } else if (isTxtFile(path)) {
-    // Load TXT file
-    auto txt = loadTxt(path);
-    if (txt) {
-      onGoToTxtReader(std::move(txt));
-    } else {
-      exitActivity();
-      enterNewActivity(new FullScreenMessageActivity(renderer, mappedInput, "Failed to load TXT",
-                                                     EpdFontFamily::REGULAR, EInkDisplay::HALF_REFRESH));
-      delay(2000);
-      onGoToFileSelection();
-    }
-  } else {
-    // Load EPUB file
-    auto epub = loadEpub(path);
-    if (epub) {
-      onGoToEpubReader(std::move(epub));
-    } else {
-      exitActivity();
-      enterNewActivity(new FullScreenMessageActivity(renderer, mappedInput, "Failed to load epub",
-                                                     EpdFontFamily::REGULAR, EInkDisplay::HALF_REFRESH));
-      delay(2000);
-      onGoToFileSelection();
-    }
-  }
-}
-
-void ReaderActivity::onGoToFileSelection(const std::string& fromBookPath) {
-  exitActivity();
+void ReaderActivity::goToLibrary(const std::string& fromBookPath) {
   // If coming from a book, start in that book's folder; otherwise start from root
   const auto initialPath = fromBookPath.empty() ? "/" : extractFolderPath(fromBookPath);
-  enterNewActivity(new FileSelectionActivity(
-      renderer, mappedInput, [this](const std::string& path) { onSelectBookFile(path); }, onGoBack, initialPath));
+  onGoToLibrary(initialPath, libraryTab);
 }
 
 void ReaderActivity::onGoToEpubReader(std::unique_ptr<Epub> epub) {
@@ -130,8 +83,7 @@ void ReaderActivity::onGoToEpubReader(std::unique_ptr<Epub> epub) {
   currentBookPath = epubPath;
   exitActivity();
   enterNewActivity(new EpubReaderActivity(
-      renderer, mappedInput, std::move(epub), [this, epubPath] { onGoToFileSelection(epubPath); },
-      [this] { onGoBack(); }));
+      renderer, mappedInput, std::move(epub), [this, epubPath] { goToLibrary(epubPath); }, [this] { onGoBack(); }));
 }
 
 void ReaderActivity::onGoToXtcReader(std::unique_ptr<Xtc> xtc) {
@@ -139,8 +91,7 @@ void ReaderActivity::onGoToXtcReader(std::unique_ptr<Xtc> xtc) {
   currentBookPath = xtcPath;
   exitActivity();
   enterNewActivity(new XtcReaderActivity(
-      renderer, mappedInput, std::move(xtc), [this, xtcPath] { onGoToFileSelection(xtcPath); },
-      [this] { onGoBack(); }));
+      renderer, mappedInput, std::move(xtc), [this, xtcPath] { goToLibrary(xtcPath); }, [this] { onGoBack(); }));
 }
 
 void ReaderActivity::onGoToTxtReader(std::unique_ptr<Txt> txt) {
@@ -148,15 +99,14 @@ void ReaderActivity::onGoToTxtReader(std::unique_ptr<Txt> txt) {
   currentBookPath = txtPath;
   exitActivity();
   enterNewActivity(new TxtReaderActivity(
-      renderer, mappedInput, std::move(txt), [this, txtPath] { onGoToFileSelection(txtPath); },
-      [this] { onGoBack(); }));
+      renderer, mappedInput, std::move(txt), [this, txtPath] { goToLibrary(txtPath); }, [this] { onGoBack(); }));
 }
 
 void ReaderActivity::onEnter() {
   ActivityWithSubactivity::onEnter();
 
   if (initialBookPath.empty()) {
-    onGoToFileSelection();  // Start from root when entering via Browse
+    goToLibrary();  // Start from root when entering via Browse
     return;
   }