Bug: PDP datastore fails to initialize with PostgreSQL backend

[frrist]

Summary

When using PostgreSQL as the database backend, piri fails to start with:

creating pdp object store: mkdir /data/piri/pdp/datastore: no such file or directory

Root Cause

The flatfs.create() function uses os.Mkdir() which only creates a single directory level. It fails if the parent directory doesn't exist.

Why it worked with SQLite:

1. ensureSQLiteDir() is called for SQLite, which uses os.MkdirAll()
2. SQLite path is /data/piri/pdp/state/state.db
3. This inadvertently creates /data/piri/pdp/ as a side effect
4. Later, PDP store creation at /data/piri/pdp/datastore succeeds because parent exists

Why it fails with PostgreSQL:

1. ensureSQLiteDir() is never called (postgres doesn't need local DB file)
2. /data/piri/pdp/ is never created
3. PDP store creation fails because os.Mkdir() can't create parent directories

Fix

In pkg/store/objectstore/flatfs/flatfs.go, line 137:

// Before
err := os.Mkdir(path, 0755)
if err != nil && !os.IsExist(err) {
    return err
}

// After
err := os.MkdirAll(path, 0755)
if err != nil {
    return err
}

os.MkdirAll() creates the entire directory tree including parents, and doesn't error if the directory already exists.

Affected Code

• pkg/store/objectstore/flatfs/flatfs.go - create() function
• Hidden dependency on SQLite initialization order

Testing

Discovered via smelt integration tests with --profile piri-postgres. All existing flatfs unit tests pass with the fix.