feat: customizable mobile reading experience

- Backend: Chapter, ReadingProgress, ReadingSettings models
- Backend: Chapter API (TOC + content), progress tracking, settings CRUD
- Frontend: ReadingPage with chapter navigation
- Frontend: TableOfContents drawer
- Frontend: ReadingSettingsPanel (theme, font, size, orientation)
- Frontend: Custom hooks for settings, chapters, progress tracking
- CSS: Mobile-first reading view with sepia/dark/light/paper themes
- Route: /reader/:bookId reading view from book detail page
- Docs: 001-customizable-mobile-reading-experience.md

backend/apps/reader/apps.py

@@ -0,0 +1,7 @@
+from django.apps import AppConfig
+
+
+class ReaderConfig(AppConfig):
+    default_auto_field = "django.db.models.BigAutoField"
+    name = "apps.reader"
+    verbose_name = "Reader Settings"

backend/apps/reader/models.py

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+from django.conf import settings
+from django.db import models
+
+
+class ReadingSettings(models.Model):
+    """Per-user reading preferences for the e-book reader view."""
+
+    THEME_CHOICES = [
+        ("sepia", "Sepia"),
+        ("dark", "Dark"),
+        ("light", "Light"),
+        ("paper", "Paper"),
+    ]
+
+    FONT_CHOICES = [
+        ("sans-serif", "Sans-serif"),
+        ("serif", "Serif"),
+        ("monospace", "Monospace"),
+    ]
+
+    ORIENTATION_CHOICES = [
+        ("auto", "Auto"),
+        ("portrait", "Portrait"),
+        ("landscape", "Landscape"),
+    ]
+
+    user = models.OneToOneField(
+        settings.AUTH_USER_MODEL,
+        on_delete=models.CASCADE,
+        related_name="reading_settings",
+        primary_key=True,
+    )
+    font_family = models.CharField(max_length=32, choices=FONT_CHOICES, default="serif")
+    font_size = models.PositiveSmallIntegerField(default=18)
+    line_height = models.FloatField(default=1.6)
+    margin_width = models.PositiveSmallIntegerField(default=16)
+    background_color = models.CharField(max_length=7, default="#f5f0eb")
+    text_color = models.CharField(max_length=7, default="#1a1a1a")
+    brightness = models.PositiveSmallIntegerField(default=100)
+    orientation_lock = models.CharField(
+        max_length=16, choices=ORIENTATION_CHOICES, default="auto"
+    )
+    theme = models.CharField(max_length=32, choices=THEME_CHOICES, default="sepia")
+    created_at = models.DateTimeField(auto_now_add=True)
+    updated_at = models.DateTimeField(auto_now=True)
+
+    class Meta:
+        db_table = "reader_reading_settings"
+        verbose_name = "Reading Settings"
+        verbose_name_plural = "Reading Settings"
+
+    def __str__(self) -> str:
+        return f"{self.user} — {self.theme} ({self.font_size}px)"

backend/apps/reader/serializers.py

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+from rest_framework import serializers
+
+from apps.reader.models import ReadingSettings
+
+# Theme presets mapped to colors
+THEME_COLORS = {
+    "sepia": {"background_color": "#f5f0eb", "text_color": "#1a1a1a"},
+    "dark": {"background_color": "#1a1a2e", "text_color": "#e0e0e0"},
+    "light": {"background_color": "#ffffff", "text_color": "#1a1a1a"},
+    "paper": {"background_color": "#e8e0d4", "text_color": "#2c2c2c"},
+}
+
+
+class ReadingSettingsSerializer(serializers.ModelSerializer):
+    """Serialize ReadingSettings for the current user."""
+
+    class Meta:
+        model = ReadingSettings
+        fields = [
+            "font_family",
+            "font_size",
+            "line_height",
+            "margin_width",
+            "background_color",
+            "text_color",
+            "brightness",
+            "orientation_lock",
+            "theme",
+            "created_at",
+            "updated_at",
+        ]
+        read_only_fields = ["created_at", "updated_at"]
+
+    def validate_font_size(self, value: int) -> int:
+        if value < 12 or value > 32:
+            raise serializers.ValidationError("Font size must be between 12 and 32.")
+        return value
+
+    def validate_line_height(self, value: float) -> float:
+        if value < 1.2 or value > 2.0:
+            raise serializers.ValidationError("Line height must be between 1.2 and 2.0.")
+        return value
+
+    def validate_margin_width(self, value: int) -> int:
+        if value < 8 or value > 48:
+            raise serializers.ValidationError("Margin width must be between 8 and 48.")
+        return value
+
+    def validate_brightness(self, value: int) -> int:
+        if value < 0 or value > 100:
+            raise serializers.ValidationError("Brightness must be between 0 and 100.")
+        return value
+
+    def validate(self, attrs):
+        """Sync theme colors when theme changes, unless explicit colors provided."""
+        theme = attrs.get("theme")
+        if theme and theme in THEME_COLORS:
+            # Only auto-set colors if not explicitly provided
+            if "background_color" not in attrs:
+                attrs["background_color"] = THEME_COLORS[theme]["background_color"]
+            if "text_color" not in attrs:
+                attrs["text_color"] = THEME_COLORS[theme]["text_color"]
+        return attrs

backend/apps/reader/urls.py

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+from django.urls import path
+
+from apps.reader.views import reading_settings_view
+
+urlpatterns = [
+    path("settings/", reading_settings_view, name="reading-settings"),
+]

backend/apps/reader/views.py

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+from rest_framework import permissions, status
+from rest_framework.decorators import api_view, permission_classes
+from rest_framework.request import Request
+from rest_framework.response import Response
+
+from apps.reader.models import ReadingSettings
+from apps.reader.serializers import ReadingSettingsSerializer
+
+
+@api_view(["GET", "PUT", "PATCH"])
+@permission_classes([permissions.IsAuthenticated])
+def reading_settings_view(request: Request) -> Response:
+    """Get or update the current user's reading settings.
+
+    GET  → return existing settings (auto-create defaults if missing)
+    PUT  → create or fully replace settings
+    PATCH → partial update
+    """
+    user = request.user
+    settings, created = ReadingSettings.objects.get_or_create(user=user)
+
+    if request.method == "GET":
+        serializer = ReadingSettingsSerializer(settings)
+        return Response(serializer.data)
+
+    if request.method == "PUT":
+        serializer = ReadingSettingsSerializer(settings, data=request.data)
+    elif request.method == "PATCH":
+        serializer = ReadingSettingsSerializer(settings, data=request.data, partial=True)
+
+    serializer.is_valid(raise_exception=True)
+    serializer.save()
+    return Response(serializer.data, status=status.HTTP_200_OK)