refactor: remove dead code and unused exports

Delete proxy-auth.ts, types/index.ts, staff-user.ts+test, local-imports.ts+test (only used by their own tests). Remove unused foundation exports: sanitizeFilename, canonicalizeFormValue, canonicalizeFormData, ConflictError, getRequestStore, getClientIp, elapsed. Remove stale TODO comments from rank-authority.ts and notice.ts. Fix biome lint warnings in catalog-repair.ts.

src/lib/foundation/errors.ts

@@ -49,14 +49,6 @@ export class RateLimitError extends DomainError {
 	}
 }
 
-// TODO: Check of dit weg kan — niet geïmporteerd in de codebase
-export class ConflictError extends DomainError {
-	constructor(message: string) {
-		super(message, 409);
-		this.name = "ConflictError";
-	}
-}
-
 export class DatabaseError extends DomainError {
 	public readonly cause: unknown;