feat: migrate tags and contributors from TEXT to TEXT[] arrays

Convert tags and contributors columns from comma-separated strings to PostgreSQL
TEXT[] arrays for better data normalization and query performance.

Database Changes:
- schema.sql: Change tags/contributors from TEXT to TEXT[]
- schema.sql: Add GIN indexes for fast array searches
- queries.sql: Update search queries to use ANY() operator
- queries.sql: Update fuzzy search with unnest() for arrays

Generated Code (sqlc):
- models.go: Auto-generated with []string types for tags/contributors
- queries.sql.go: Auto-generated with proper array handling

Handler Changes:
- media.go: Update request structs to use []string for tags/contributors
- media.go: Remove pgtype.Text wrapping, use direct array assignment
- media.go: Add tag normalization in CreateMediaItemHandler
- collections.go: Update tags evaluation to join arrays for comparison
- collections.go: Add strings import for Join() function

Service Changes:
- ebook_scanner.go: Update EbookMetadata struct to use []string
- ebook_scanner.go: Remove string Join(), assign arrays directly
- collection_service.go: Update tags rule evaluation to join arrays
- collection_service.go: Add strings import

New Utilities:
- internal/utils/tags.go: Create NormalizeTags(), JoinTags(), SplitTags()
- Normalizes tags by trimming, lowercasing, removing duplicates/empties

API Documentation:
- bruno/media-items/Create Media Item.bru: Update examples to use arrays
- bruno/media-items/Update Media Item.bru: Update examples to use arrays
- Update docs: tags/contributors now array of string

Breaking Change:
- JSON format changes from "tags": "tag1,tag2" to "tags": ["tag1", "tag2"]
- Tests already use array format (no changes needed)

Benefits:
- GIN indexes enable faster array searches
- Normalization prevents data quality issues (case, duplicates)
- Array operations use PostgreSQL native operators (ANY, &&, unnest)
- Better separation of concerns (no string parsing in application)

internal/services/ebook_scanner.go

@@ -41,11 +41,11 @@ type EbookMetadata struct {
 	SeriesNumber int32
 	Publisher    string
 	PublishDate  time.Time
-	Contributors string
+	Contributors []string
 	CoverPath    string
 	ISBN         string
 	ASIN         string
-	Tags         string
+	Tags         []string
 
 	Phase1HashInfo      *HashInfo
 	Phase1FormatFormats []*FormatInfo
@@ -468,8 +468,8 @@ func (s *EbookScanner) processEbookFile(ctx context.Context, path string) error
 		SeriesNumber:   pgtype.Int4{Int32: metadata.SeriesNumber, Valid: metadata.SeriesNumber > 0},
 		Publisher:      pgtype.Text{String: metadata.Publisher, Valid: metadata.Publisher != ""},
 		DatePublished:  pgtype.Date{Time: metadata.PublishDate, Valid: !metadata.PublishDate.IsZero()},
-		Contributors:   pgtype.Text{String: metadata.Contributors, Valid: metadata.Contributors != ""},
-		Tags:           pgtype.Text{String: metadata.Tags, Valid: metadata.Tags != ""},
+		Contributors:   metadata.Contributors,
+		Tags:           metadata.Tags,
 		AddedByAdminID: s.adminID,
 	})
 	if err != nil {
@@ -576,7 +576,8 @@ func (s *EbookScanner) extractEPUBMetadata(path string) (*EbookMetadata, error)
 
 	// Contributors
 	if contributors, err := book.MetadataByKey("contributor"); err == nil && len(contributors) > 0 {
-		metadata.Contributors = strings.Join(contributors, ", ")
+		// Already a []string from xml parsing, just assign
+		metadata.Contributors = contributors
 	}
 
 	// ISBN
@@ -602,7 +603,8 @@ func (s *EbookScanner) extractEPUBMetadata(path string) (*EbookMetadata, error)
 
 	// Tags
 	if tags, err := book.MetadataByKey("subject"); err == nil && len(tags) > 0 {
-		metadata.Tags = strings.Join(tags, ", ")
+		// Already a []string from xml parsing, just assign
+		metadata.Tags = tags
 	}
 
 	return metadata, nil