fix: cascade-clean ignored/blocked rows on hard contact delete

hard_delete_contact() failed with FOREIGN KEY constraint when the
contact had a row in ignored_contacts or blocked_contacts, since those
FKs lacked ON DELETE CASCADE. Delete dependent rows first in the same
transaction; also update schema for new deployments.

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

app/database.py

@@ -197,12 +197,16 @@ class Database:
             return cursor.rowcount > 0
 
     def hard_delete_contact(self, public_key: str) -> bool:
-        """Permanently delete a contact from the database."""
+        """Permanently delete a contact from the database.
+
+        Also clears ignored/blocked rows that reference this contact
+        via FK without ON DELETE CASCADE.
+        """
+        pk = public_key.lower()
         with self._connect() as conn:
-            cursor = conn.execute(
-                "DELETE FROM contacts WHERE public_key = ?",
-                (public_key.lower(),)
-            )
+            conn.execute("DELETE FROM ignored_contacts WHERE public_key = ?", (pk,))
+            conn.execute("DELETE FROM blocked_contacts WHERE public_key = ?", (pk,))
+            cursor = conn.execute("DELETE FROM contacts WHERE public_key = ?", (pk,))
             return cursor.rowcount > 0
 
     def downgrade_stale_device_contacts(self, active_device_keys: set) -> int:

app/schema.sql

@@ -152,13 +152,13 @@ CREATE TABLE IF NOT EXISTS read_status (
 
 -- Ignored contacts (adverts cached but not pending/auto-added)
 CREATE TABLE IF NOT EXISTS ignored_contacts (
-    public_key  TEXT PRIMARY KEY REFERENCES contacts(public_key),
+    public_key  TEXT PRIMARY KEY REFERENCES contacts(public_key) ON DELETE CASCADE,
     created_at  TEXT NOT NULL DEFAULT (datetime('now'))
 );
 
 -- Blocked contacts (ignored + messages hidden from display)
 CREATE TABLE IF NOT EXISTS blocked_contacts (
-    public_key  TEXT PRIMARY KEY REFERENCES contacts(public_key),
+    public_key  TEXT PRIMARY KEY REFERENCES contacts(public_key) ON DELETE CASCADE,
     created_at  TEXT NOT NULL DEFAULT (datetime('now'))
 );