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/handlers/collections.go

@@ -676,8 +676,8 @@ func (h *CollectionHandler) evaluateRule(item database.ListMediaItemsRow, field,
 			itemValue = fmt.Sprintf("%d", item.CopyrightYear.Int32)
 		}
 	case "tags":
-		if item.Tags.Valid {
-			itemValue = item.Tags.String
+		if len(item.Tags) > 0 {
+			itemValue = strings.Join(item.Tags, ", ")
 		}
 	}