feat: add reader infrastructure - Phase 0 database schema and queries

Implement Phase 0 prerequisites for reader functionality including
database schema, SQL queries, and frontend dependencies.

## Database Schema (5 New Tables + 1 Column Addition)

### New Tables Added:
1. **panel_data** - Comic/manga panel detection results
   - Stores detected panel boundaries (x, y, width, height)
   - Supports grid, ML, and manual detection methods
   - JSONB storage for flexible panel structures

2. **reading_speed** - User reading speed statistics
   - Tracks pages per minute and total reading time
   - Per-user per-media-item tracking
   - Enables progress estimation and analytics

3. **dictionary_cache** - Offline dictionary word definitions
   - Caches external dictionary lookups
   - Reduces API calls and improves performance
   - Supports offline reading functionality

4. **reader_settings** - User reader preferences (per-user)
   - Stores typography, theme, and display settings
   - JSONB storage for flexible configuration
   - Per-user customization (fonts, margins, themes)

5. **media_bookmarks** - Enhanced bookmarks with chapter/CFI support
   - Unified bookmarking for ebooks, comics, manga, PDFs
   - Supports page_number, chapter_number, and epubcfi_position
   - Includes notes field for annotations
   - Unique constraint on (media_item_id, user_id, title)

### Column Addition:
- **media_items.chapter_metadata** (JSONB) - Caches detected chapter structure
  - Stores TOC/chapter detection results
  - Prevents re-parsing files on every read
  - Populated by ReaderService.DetectChapters()

## Database Queries (12 New Queries)

Added queries for all reader functionality:
- Panel data: GetPanelData, UpsertPanelData
- Reading speed: GetReadingSpeed, CreateReadingSpeed, UpdateReadingSpeed
- Dictionary: GetDictionaryEntry, CreateDictionaryEntry, UpdateDictionaryAccessed
- Settings: GetReaderSettings, UpsertReaderSettings
- Bookmarks: GetMediaBookmarks, CreateMediaBookmark, DeleteMediaBookmark, UpdateMediaBookmark

## Frontend Dependencies

Added to package.json:
- jszip@^3.10.1 - EPUB/comic archive parsing (client-side)
- pdfjs-dist@^3.11.174 - PDF rendering library (Mozilla PDF.js)

## Generated Code

Ran `sqlc generate` to regenerate:
- models.go - Go structs for new tables (55 lines added)
- querier.go - Database query methods (14 lines added)
- queries.sql.go - Compiled SQL queries (504 lines added)

## Implementation Status

Phase 0 prerequisites now complete:
✅ Database schema (5 tables + 1 column)
✅ SQL queries (12 queries)
✅ Frontend dependencies (2 packages)
✅ Generated Go code (sqlc)
✅ Database recreated with new schema

Ready for Phase 1: Infrastructure & Basic Reader implementation.

Related to: Universal web reader for ebooks, comics, manga, PDFs

internal/database/queries/queries.sql

@@ -1924,3 +1924,89 @@ RETURNING *;
 DELETE FROM saved_filters
 WHERE id = @id AND user_id = @user_id
 RETURNING *;
+
+-- name: GetPanelData :one
+SELECT * FROM panel_data
+WHERE media_item_id = $1 AND page_number = $2;
+
+-- name: UpsertPanelData :one
+INSERT INTO panel_data (media_item_id, page_number, detection_method, panels)
+VALUES ($1, $2, $3, $4)
+ON CONFLICT (media_item_id, page_number)
+DO UPDATE SET
+    detection_method = EXCLUDED.detection_method,
+    panels = EXCLUDED.panels,
+    updated_at = NOW()
+RETURNING *;
+
+-- name: GetReadingSpeed :one
+SELECT * FROM reading_speed
+WHERE user_id = $1 AND media_item_id = $2;
+
+-- name: CreateReadingSpeed :one
+INSERT INTO reading_speed (user_id, media_item_id, pages_per_minute, pages_read, total_reading_minutes, last_read_at)
+VALUES ($1, $2, $3, $4, $5, $6)
+RETURNING *;
+
+-- name: UpdateReadingSpeed :one
+UPDATE reading_speed
+SET
+    pages_per_minute = $3,
+    pages_read = pages_read + $4,
+    total_reading_minutes = total_reading_minutes + $5,
+    last_read_at = $6,
+    updated_at = NOW()
+WHERE user_id = $1 AND media_item_id = $2
+RETURNING *;
+
+-- name: GetDictionaryEntry :one
+SELECT * FROM dictionary_cache
+WHERE word = $1;
+
+-- name: CreateDictionaryEntry :one
+INSERT INTO dictionary_cache (word, definition, part_of_speech, example, etymology, accessed_at)
+VALUES ($1, $2, $3, $4, $5, NOW())
+RETURNING *;
+
+-- name: UpdateDictionaryAccessed :one
+UPDATE dictionary_cache
+SET accessed_at = NOW()
+WHERE word = $1
+RETURNING *;
+
+-- name: GetReaderSettings :one
+SELECT setting_value FROM reader_settings
+WHERE user_id = $1 AND setting_key = 'reader_settings';
+
+-- name: UpsertReaderSettings :one
+INSERT INTO reader_settings (user_id, setting_key, setting_value)
+VALUES ($1, 'reader_settings', $2)
+ON CONFLICT (user_id, setting_key)
+DO UPDATE SET
+    setting_value = EXCLUDED.setting_value,
+    updated_at = NOW()
+RETURNING *;
+
+-- name: GetMediaBookmarks :many
+SELECT * FROM media_bookmarks
+WHERE media_item_id = $1 AND user_id = $2
+ORDER BY created_at DESC;
+
+-- name: CreateMediaBookmark :one
+INSERT INTO media_bookmarks (media_item_id, user_id, page_number, chapter_number, cfi_position, title, position, notes)
+VALUES ($1, $2, $3, $4, $5, $6, $7, $8)
+RETURNING *;
+
+-- name: DeleteMediaBookmark :exec
+DELETE FROM media_bookmarks
+WHERE id = $1;
+
+-- name: UpdateMediaBookmark :one
+UPDATE media_bookmarks
+SET
+    title = $2,
+    notes = $3,
+    position = $4,
+    updated_at = NOW()
+WHERE id = $1 AND user_id = $5
+RETURNING *;