feat(database): add file size metadata and range parameters

- Add byte_size and line_count columns to files table
- Increment SchemaVersion to 2 (requires re-indexing)
- Add DeclarationWithMetadata, FileRange, FileResult types
- Add GetDeclarationsWithMetadata method for file metadata lookup
- Add GetFileWithRange method for paginated file retrieval
- Implement countLines and applyLineRange helpers

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

internal/database/schema.go

@@ -2,7 +2,7 @@ package database
 
 // SchemaVersion is the current database schema version.
 // When this changes, the database will be dropped and recreated.
-const SchemaVersion = 1
+const SchemaVersion = 2
 
 // Common SQL statements shared between implementations.
 const (
@@ -53,7 +53,9 @@ const (
 			revision_id INTEGER NOT NULL REFERENCES revisions(id) ON DELETE CASCADE,
 			file_path TEXT NOT NULL,
 			extension TEXT,
-			content TEXT NOT NULL
+			content TEXT NOT NULL,
+			byte_size INTEGER NOT NULL DEFAULT 0,
+			line_count INTEGER NOT NULL DEFAULT 0
 		)`
 )