feat(store): add account from_address field + v2 migration

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

internal/store/schema.go

@@ -1,8 +1,8 @@
 package store
 
-const schemaVersion = 1
+const schemaVersion = 2
 
-// schemaSQL is the full v1 schema. All statements are idempotent via IF NOT EXISTS.
+// schemaSQL is the full current schema. All statements are idempotent via IF NOT EXISTS.
 const schemaSQL = `
 CREATE TABLE IF NOT EXISTS settings (
   key   TEXT PRIMARY KEY,
@@ -21,6 +21,7 @@ CREATE TABLE IF NOT EXISTS accounts (
   smtp_security           TEXT,
   auth_type               TEXT NOT NULL CHECK (auth_type IN ('password','oauth2')),
   username                TEXT NOT NULL,
+  from_address            TEXT,
   enc_password            BLOB,
   enc_oauth_client_id     BLOB,
   enc_oauth_client_secret BLOB,