By Ananya Mariam Rajesh and Helen Reid (Reuters) -Birkenstock warned on Thursday annual earnings would come under pressure as the German footwear maker embarks on a global expansion, disappointing investors with its first results since its IPO and sending shares tumbling as much as 14%. Executives on a call said the company planned to raise prices on its sandals and clogs this year after it had “underestimated the inflation effects” in fiscal 2023. Birkenstock expects adjusted earnings before interest, taxes, depreciation, and amortization (EBITDA) margin of about 30% for 2024, citing a “modes…