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)

bruno/media-items/Create Media Item.bru

@@ -23,11 +23,11 @@ body:json {
   "cover_image_path": "/path/to/cover.jpg",
   "series": "Series Name",
   "series_number": 1,
-  "tags": "fiction, adventure",
+  "tags": ["fiction", "adventure"],
   "asin": "B08XYZ123",
   "date_published": "2023-01-15",
   "publisher": "Publisher Name",
-  "contributors": "Contributor Name",
+  "contributors": ["Contributor Name"],
   "language": "en",
   "edition": "First Edition",
   "page_count": 350,
@@ -93,11 +93,11 @@ docs {
   - `cover_image_path` (string, optional): Path to cover image
   - `series` (string, optional): Series name
   - `series_number` (integer, optional): Number in series
-  - `tags` (string, optional): Tags or categories
+  - `tags` (array of string, optional): Tags or categories
   - `asin` (string, optional): Amazon ASIN
   - `date_published` (string, optional): Publication date
   - `publisher` (string, optional): Publisher name
-  - `contributors` (string, optional): Contributors
+  - `contributors` (array of string, optional): List of contributors
   - `language` (string, optional): Language code (ISO 639-1)
   - `edition` (string, optional): Edition information
   - `page_count` (integer, optional): Total page count

bruno/media-items/Update Media Item.bru

@@ -22,11 +22,11 @@ body:json {
   "cover_image_path": "/updated/path/to/cover.jpg",
   "series": "Updated Series Name",
   "series_number": 2,
-  "tags": "updated, fiction, adventure",
+  "tags": ["updated", "fiction", "adventure"],
   "asin": "B09XYZ789",
   "date_published": "2023-02-20",
   "publisher": "Updated Publisher",
-  "contributors": "Updated Contributor",
+  "contributors": ["Updated Contributor"],
   "language": "en",
   "edition": "Updated Edition",
   "page_count": 400,