chore: reconcile Plan 1A branch with idfoto→relicario rename

Renames crate directories and sweeps identifiers so Plan 1B can reference
the post-rename names throughout.

- git mv crates/idfoto-{core,cli,wasm} → crates/relicario-{core,cli,wasm}
- sed sweep: idfoto_core/idfoto-core/IdfotoError/IDFOTO_IMAGE/.idfoto/ etc.
- All 128 relicario-core tests pass post-sweep

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

crates/relicario-core/tests/attachments.rs

@@ -0,0 +1,52 @@
+//! Attachment encrypt/decrypt + content-addressed AID + cap enforcement.
+
+use relicario_core::{
+    AttachmentId, RelicarioError,
+    crypto::KdfParams,
+    decrypt_attachment, derive_master_key, encrypt_attachment,
+};
+use zeroize::Zeroizing;
+
+fn fast_params() -> KdfParams { KdfParams { argon2_m: 256, argon2_t: 1, argon2_p: 1 } }
+
+fn make_key() -> Zeroizing<[u8; 32]> {
+    derive_master_key(b"x", &[0u8; 32], &[0u8; 32], &fast_params()).unwrap()
+}
+
+#[test]
+fn attachment_round_trip_5kb() {
+    let plaintext: Vec<u8> = (0..5000u32).map(|i| (i & 0xff) as u8).collect();
+    let key = make_key();
+    let enc = encrypt_attachment(&plaintext, &key, 10 * 1024 * 1024).unwrap();
+    assert_eq!(enc.id, AttachmentId::from_plaintext(&plaintext));
+
+    let dec = decrypt_attachment(&enc.bytes, &key).unwrap();
+    assert_eq!(&*dec, &plaintext);
+}
+
+#[test]
+fn identical_plaintexts_yield_identical_aids() {
+    let plaintext = b"hello world";
+    let key = make_key();
+    let a = encrypt_attachment(plaintext, &key, 1024).unwrap();
+    let b = encrypt_attachment(plaintext, &key, 1024).unwrap();
+    assert_eq!(a.id, b.id);
+    // (Bytes will differ because nonce is random per-encryption — that's expected.)
+}
+
+#[test]
+fn cap_enforcement_at_exact_max() {
+    let plaintext = vec![0u8; 1024];
+    let key = make_key();
+    // Exactly at max — should pass
+    let _ = encrypt_attachment(&plaintext, &key, 1024).unwrap();
+    // One byte over — should fail
+    let err = encrypt_attachment(&plaintext, &key, 1023);
+    match err {
+        Err(RelicarioError::AttachmentTooLarge { size, max }) => {
+            assert_eq!(size, 1024);
+            assert_eq!(max, 1023);
+        }
+        other => panic!("expected AttachmentTooLarge, got {other:?}"),
+    }
+}