mod: Phase 1 - bring forward mod-exclusive files with ActivityManager migration

Brings ~55 mod-exclusive files to the upstream-based mod/master-resync branch:

Activities (migrated to new ActivityManager pattern):
- Clock/Time: SetTimeActivity, SetTimezoneOffsetActivity, NtpSyncActivity
- Dictionary: DictionaryDefinitionActivity, DictionarySuggestionsActivity,
  DictionaryWordSelectActivity, LookedUpWordsActivity
- Bookmark: EpubReaderBookmarkSelectionActivity
- Book management: BookManageMenuActivity, EndOfBookMenuActivity
- OPDS: OpdsServerListActivity, OpdsSettingsActivity
- Utility: DirectoryPickerActivity, NumericStepperActivity

Utilities (unchanged):
- BookManager, BookSettings, BookmarkStore, BootNtpSync
- Dictionary, LookupHistory, TimeSync, OpdsServerStore

Libraries: PlaceholderCover, TableData, ChapterXPathIndexer
Scripts: inject_mod_version, generate_book_icon, preview_placeholder_cover
Docs: KOReader sync XPath mapping

Migration changes:
- ActivityWithSubactivity -> Activity base class
- Callback constructors -> finish()/setResult() pattern
- enterNewActivity() -> startActivityForResult()
- Activity::RenderLock&& -> RenderLock&&

These files won't compile yet - they reference mod settings and I18n
strings that will be added in subsequent phases.

Made-with: Cursor

scripts/generate_book_icon.py

@@ -0,0 +1,123 @@
+#!/usr/bin/env python3
+"""Generate a 1-bit book icon bitmap as a C header for PlaceholderCoverGenerator.
+
+The icon is a simplified closed book with a spine on the left and 3 text lines.
+Output format matches Logo120.h: MSB-first packed 1-bit, 0=black, 1=white.
+"""
+
+from PIL import Image, ImageDraw
+import sys
+
+
+def generate_book_icon(size=48):
+    """Create a book icon at the given size."""
+    img = Image.new("1", (size, size), 1)  # White background
+    draw = ImageDraw.Draw(img)
+
+    # Scale helper
+    s = size / 48.0
+
+    # Book body (main rectangle, leaving room for spine and pages)
+    body_left = int(6 * s)
+    body_top = int(2 * s)
+    body_right = int(42 * s)
+    body_bottom = int(40 * s)
+
+    # Draw book body outline (2px thick)
+    for i in range(int(2 * s)):
+        draw.rectangle(
+            [body_left + i, body_top + i, body_right - i, body_bottom - i], outline=0
+        )
+
+    # Spine (thicker left edge)
+    spine_width = int(4 * s)
+    draw.rectangle([body_left, body_top, body_left + spine_width, body_bottom], fill=0)
+
+    # Pages at the bottom (slight offset from body)
+    pages_top = body_bottom
+    pages_bottom = int(44 * s)
+    draw.rectangle(
+        [body_left + int(2 * s), pages_top, body_right - int(1 * s), pages_bottom],
+        outline=0,
+    )
+    # Page edges (a few lines)
+    for i in range(3):
+        y = pages_top + int((i + 1) * 1 * s)
+        if y < pages_bottom:
+            draw.line(
+                [body_left + int(3 * s), y, body_right - int(2 * s), y], fill=0
+            )
+
+    # Text lines on the book cover
+    text_left = body_left + spine_width + int(4 * s)
+    text_right = body_right - int(4 * s)
+    line_thickness = max(1, int(1.5 * s))
+
+    text_lines_y = [int(12 * s), int(18 * s), int(24 * s)]
+    text_widths = [1.0, 0.7, 0.85]  # Relative widths for visual interest
+
+    for y, w_ratio in zip(text_lines_y, text_widths):
+        line_right = text_left + int((text_right - text_left) * w_ratio)
+        for t in range(line_thickness):
+            draw.line([text_left, y + t, line_right, y + t], fill=0)
+
+    return img
+
+
+def image_to_c_array(img, name="BookIcon"):
+    """Convert a 1-bit PIL image to a C header array."""
+    width, height = img.size
+    pixels = img.load()
+
+    bytes_per_row = width // 8
+    data = []
+
+    for y in range(height):
+        for bx in range(bytes_per_row):
+            byte = 0
+            for bit in range(8):
+                x = bx * 8 + bit
+                if x < width:
+                    # 1 = white, 0 = black (matching Logo120.h convention)
+                    if pixels[x, y]:
+                        byte |= 1 << (7 - bit)
+            data.append(byte)
+
+    # Format as C header
+    lines = []
+    lines.append("#pragma once")
+    lines.append("#include <cstdint>")
+    lines.append("")
+    lines.append(f"// Book icon: {width}x{height}, 1-bit packed (MSB first)")
+    lines.append(f"// 0 = black, 1 = white (same format as Logo120.h)")
+    lines.append(f"static constexpr int BOOK_ICON_WIDTH = {width};")
+    lines.append(f"static constexpr int BOOK_ICON_HEIGHT = {height};")
+    lines.append(f"static const uint8_t {name}[] = {{")
+
+    # Format data in rows of 16 bytes
+    for i in range(0, len(data), 16):
+        chunk = data[i : i + 16]
+        hex_str = ", ".join(f"0x{b:02x}" for b in chunk)
+        lines.append(f"    {hex_str},")
+
+    lines.append("};")
+    lines.append("")
+
+    return "\n".join(lines)
+
+
+if __name__ == "__main__":
+    size = int(sys.argv[1]) if len(sys.argv) > 1 else 48
+    img = generate_book_icon(size)
+
+    # Save preview PNG
+    preview_path = f"mod/book_icon_{size}x{size}.png"
+    img.resize((size * 4, size * 4), Image.NEAREST).save(preview_path)
+    print(f"Preview saved to {preview_path}", file=sys.stderr)
+
+    # Generate C header
+    header = image_to_c_array(img, "BookIcon")
+    output_path = "lib/PlaceholderCover/BookIcon.h"
+    with open(output_path, "w") as f:
+        f.write(header)
+    print(f"C header saved to {output_path}", file=sys.stderr)