fix(ebook-reader): Replace ReflowableBook with UniversalReader type system

BREAKING CHANGE: Unify ebook reader type system to match actual data structures

Problem:
- ReflowableBook type had direct properties (spine, resources, toc, metadata)
- UniversalReader wraps EbookCIF in cif property with runtime state
- Type mismatch caused unsafe 'as any' casts and runtime errors
- Two conflicting UniversalReader definitions existed (reader-shell vs reader-context)

Root Cause:
- Parsers return EbookCIF (nested structure)
- ReflowableBook expected flat structure
- Code mixed both approaches causing confusion

Changes:

Type System Updates:
- Replace all ReflowableBook references with UniversalReader
- Remove duplicate UniversalReader definition in reader-context.ts
- Import UniversalReader from canonical source (reader-shell.ts)
- Update all function signatures across reflowable module

Property Access Patterns:
- book.cif.spine instead of book.spine
- book.cif.resources instead of book.resources
- book.cif.toc instead of book.toc
- book.cif.metadata instead of book.metadata

Fixed Modules:
- reader-shell.ts: UniversalReader object construction
- reader-context.ts: Remove duplicate interface, import from reader-shell
- reader-navigation.ts: Remove unsafe type casts, fix property access
- reader-services.ts: Align with UniversalReader structure
- reflowable/navigation.ts: Update all navigation function signatures
- reflowable/progress-tracker.ts: Update tracker function signatures
- reflowable/parser.ts: Return UniversalReader with proper structure
- reflowable/page-calculator.ts: Update calculation function signatures
- reflowable/ebook/search.ts: Fix property access patterns
- types/reader.d.ts: Remove duplicate type definitions

Impact:
- ✅ Type-safe throughout ebook reader
- ✅ Matches actual data structures from parsers
- ✅ No more unsafe type casts
- ✅ Single source of truth for UniversalReader
- ✅ Aligns with EbookCIF format from API/parsers

Files changed: 10
Lines changed: +320, -180

web/src/reader/formats/reflowable/progress-tracker.ts

@@ -1,12 +1,13 @@
 // Import types
-import type { ReflowableBook, ReadingPosition } from "./types";
+import type { ReadingPosition } from "./types";
 import { findPageByCFI, createPositionFromPage } from "./page-calculator";
+import { UniversalReader } from "../../reader-shell";
 
 // Update current position
 export function updateCurrentPosition(
-  book: ReflowableBook,
+  book: UniversalReader,
   position: ReadingPosition,
-): ReflowableBook {
+): UniversalReader {
   return {
     ...book,
     position,
@@ -14,12 +15,12 @@ export function updateCurrentPosition(
 }
 
 // Extract CFI from position
-export function getCurrentCFI(book: ReflowableBook): string {
+export function getCurrentCFI(book: UniversalReader): string {
   return book.position.cfi;
 }
 
 // Calculate progress for display
-export function calculateProgress(book: ReflowableBook): {
+export function calculateProgress(book: UniversalReader): {
   currentPage: number;
   totalPages: number;
   percentage: number;
@@ -33,7 +34,7 @@ export function calculateProgress(book: ReflowableBook): {
 }
 
 // Get position for saving to database
-export function getPositionForSave(book: ReflowableBook): {
+export function getPositionForSave(book: UniversalReader): {
   cfi: string;
   progress: number;
   page: number;
@@ -47,7 +48,7 @@ export function getPositionForSave(book: ReflowableBook): {
 
 // Restore position from database
 export function restorePosition(
-  book: ReflowableBook,
+  book: UniversalReader,
   savedCFI: string,
   savedPage?: number,
 ): ReadingPosition {