refactor: remove Phase X terminology from source code comments

Remove planning document phase references from code comments:

app_test.go:
- Remove Phase 5 references from 8 test function comments

querier.go & queries.sql.go:
- Remove Phase 1, 2, 3, 4, 6 references from section headers
- Clean up week numbers (Weeks 5-6, Week 3-4, etc.)

queries.sql:
- Remove Phase 4 references from Kobo queries

kobo.go:
- Remove Phase 6 references from ContentId mapping comments

progress.go:
- Remove Phase 1 reference from route comment

media_scanner.go & media_scanner_library_type_test.go:
- Remove Phase 2 references from library type scanning comments

schema.sql:
- Remove Phase 1, 2, 3, 4, 5, 7 references from table/section comments
- Clean up: Format Detection, Progress Tracking, Device Registry,
  Sync Queue, Conflict Resolution, Reading History, Indexes, etc.

test_helpers.go:
- Remove Phase 6 reference from handler setup comment

These phase numbers were from internal planning documents and have no
meaning in the codebase. Removing them makes the code self-documenting.

internal/database/queries.sql.go

@@ -60,7 +60,7 @@ type AddBookToKoboShelfParams struct {
 }
 
 // ============================================
-// KOBO SHELF MANAGEMENT QUERIES (Phase 4)
+// KOBO SHELF MANAGEMENT QUERIES
 // ============================================
 func (q *Queries) AddBookToKoboShelf(ctx context.Context, arg AddBookToKoboShelfParams) (KoboShelves, error) {
 	row := q.db.QueryRow(ctx, AddBookToKoboShelf,
@@ -292,7 +292,7 @@ type CreateDeviceParams struct {
 }
 
 // ============================================
-// PHASE 2: DEVICE MANAGEMENT & AUTH (Weeks 5-6)
+// DEVICE MANAGEMENT & AUTH
 // ============================================
 // Device Registration & Management
 func (q *Queries) CreateDevice(ctx context.Context, arg CreateDeviceParams) (Devices, error) {
@@ -837,7 +837,7 @@ type CreateOrUpdateKoboEntitlementParams struct {
 }
 
 // ============================================
-// KOBO ENTITLEMENT QUERIES (Phase 4)
+// KOBO ENTITLEMENT QUERIES
 // ============================================
 func (q *Queries) CreateOrUpdateKoboEntitlement(ctx context.Context, arg CreateOrUpdateKoboEntitlementParams) (KoboEntitlements, error) {
 	row := q.db.QueryRow(ctx, CreateOrUpdateKoboEntitlement,
@@ -1084,7 +1084,7 @@ type CreateUnlinkedBookParams struct {
 }
 
 // ============================================
-// PHASE 6: ENHANCED KOBO SYNC (Week 3-4)
+// ENHANCED KOBO SYNC
 // ============================================
 // Create unlinked book entry
 func (q *Queries) CreateUnlinkedBook(ctx context.Context, arg CreateUnlinkedBookParams) (UnlinkedBooks, error) {
@@ -2902,7 +2902,7 @@ SELECT id, library_id, title, author, isbn, description, file_path, file_size, m
 `
 
 // ============================================
-// PHASE 3: KOREADER SYNC PROTOCOL (Weeks 7-9)
+// KOREADER SYNC PROTOCOL
 // ============================================
 func (q *Queries) GetMediaItemByFilePathForSync(ctx context.Context, filePath string) (MediaItems, error) {
 	row := q.db.QueryRow(ctx, GetMediaItemByFilePathForSync, filePath)
@@ -3407,8 +3407,8 @@ func (q *Queries) GetMediaRatings(ctx context.Context, mediaItemID pgtype.UUID)
 }
 
 const GetNextRetryTime = `-- name: GetNextRetryTime :one
-SELECT 
-    CASE 
+SELECT
+    CASE
         WHEN attempts = 0 THEN NOW()
         WHEN attempts = 1 THEN NOW() + INTERVAL '1 minute'
         WHEN attempts = 2 THEN NOW() + INTERVAL '5 minutes'
@@ -4053,7 +4053,7 @@ func (q *Queries) GetUnlinkedBooksByDevice(ctx context.Context, deviceID pgtype.
 }
 
 const GetUser = `-- name: GetUser :one
-SELECT 
+SELECT
     u.id,
     u.email,
     u.username,
@@ -4602,7 +4602,7 @@ const IncrementSyncQueueAttempts = `-- name: IncrementSyncQueueAttempts :one
 UPDATE sync_queue
 SET
     attempts = attempts + 1,
-    status = CASE 
+    status = CASE
         WHEN attempts + 1 >= max_attempts THEN 'failed'
         ELSE 'pending'
     END,
@@ -4716,7 +4716,7 @@ func (q *Queries) LinkUnlinkedBook(ctx context.Context, arg LinkUnlinkedBookPara
 }
 
 const ListAllSyncQueueItems = `-- name: ListAllSyncQueueItems :many
-SELECT 
+SELECT
     sq.id, sq.device_id, sq.media_item_id, sq.sync_type, sq.sync_data, sq.priority, sq.attempts, sq.max_attempts, sq.status, sq.error_message, sq.created_at, sq.processed_at,
     d.device_name,
     d.device_type,
@@ -5776,7 +5776,7 @@ func (q *Queries) ListUnresolvedUnlinkedBooks(ctx context.Context, arg ListUnres
 }
 
 const ListUsers = `-- name: ListUsers :many
-SELECT 
+SELECT
     u.id,
     u.email,
     u.username,
@@ -7175,7 +7175,7 @@ type UpdateMediaItemFormatGroupParams struct {
 }
 
 // ============================================
-// PHASE 1: FORMAT DETECTION & PROGRESS (Week 2)
+// FORMAT DETECTION & PROGRESS
 // ============================================
 // Update media item format group information
 func (q *Queries) UpdateMediaItemFormatGroup(ctx context.Context, arg UpdateMediaItemFormatGroupParams) error {
@@ -7215,7 +7215,7 @@ type UpdateMediaItemIdentifiersParams struct {
 
 // Media Items Admin Operations
 // ============================================
-// PHASE 1: UNIVERSAL BOOK IDENTIFIERS (Week 1)
+// UNIVERSAL BOOK IDENTIFIERS
 // ============================================
 // Update media item with universal identifiers
 func (q *Queries) UpdateMediaItemIdentifiers(ctx context.Context, arg UpdateMediaItemIdentifiersParams) (MediaItems, error) {