The rapid adoption of large language models (LLMs) has expanded opportunities for natural language-based programming, lowering barriers to developing digital tools through AI-assisted coding. This study examined how a short-term, project-based course in which preservice secondary mathematics teachers developed Streamlit web applications using GitHub Codespaces and Copilot and designed mathematics lessons incorporating their tools influenced their TPACK-P (Technological Pedagogical Content Knowledge-Programming). Participants were 24 second-year pre-service mathematics teachers at a university in Daejeon, South Korea. Using a pre-post design, changes in eight subdomains (PK, CK, TK, PCK, TCK, TPK, TPACK, and TPACK-P) were analyzed through reliability checks, paired-samples t-tests, K-means clustering of standardized gain scores, conceptual network analysis, and coding of open-ended responses. Findings showed significant increases in all subdomains except PK, with the largest gains in CK, TCK, and TPACK-P. Cluster analysis identified balanced growth, high-growth integrative, and partial-growth profiles, indicating heterogeneous development among participants. Network analysis revealed an integrated growth structure centered on TPACK, with strong links among TK, TCK, and TPACK, and a direct connection between TPACK-P and TCK. Overall, the results suggest that natural language-based programming can help pre-service teachers reconceptualize web application development as a productive component of mathematics lesson design while supporting differentiated growth pathways.