Create paste api

[tylerhwang333-glitch]

modules/sqlite_helpers.py

• Added two new functions:
  • insert_text_paste(sqlite_file), inserts a default row into pastes, returns the new id (lastrowid), or None on error.
  • paste_exists(sqlite_file, paste_id), checks if a given id exists in pastes.
    server.py
• Added imports: PlainTextResponse, pathlib.Path, os.
  id, writes the text to pastes/ on disk, returns {"id": paste_id}.
• Added GET /paste/view/{paste_id}: reads pastes/<paste_id> from disk and returns it as plain text, 404 if missing.