Align architecture/database.md with current java-tron storage layer and Toolkit behavior

[abn2357]

Summary

Audited docs/architecture/database.md against the current java-tron
storage layer and the Toolkit.jar db subcommands. Fixes a few
inaccuracies and fills in the gaps a reader naturally hits when
looking at the example storage { ... } block.

Notable corrections:

• db convert is x86_64-only: DbConvert.java checks
  Arch.isArm64() at the top of call() and exits early with an
  "unsupported architecture" message, so it does nothing on arm64.
  Surfaced this as a note at the start of the migration section.
• Positional, not named, arguments: section 2 previously
  documented src_db_path / dst_db_path as if they were CLI flags,
  but DbConvert.java declares them as picocli @Parameters with
  index = "0" / index = "1". Renamed the section to "Positional
  Arguments", switched to <src> / <dst> placeholders, and added
  the explicit db convert <src> <dst> command shape.
• Dropped stale legacy link: the trailing
  Rocksdb_vs_Leveldb.md link pointed at the legacy
  tronprotocol/documentation repo, which is no longer maintained.

Filled-in gaps under the storage { ... } example block:

• db.sync: explained that it controls whether the underlying
  engine waits for each write to be physically flushed to disk
  before returning. Default false. Verified that all four call
  sites — LevelDbDataSourceImpl, db2/common/LevelDB,
  db2/common/RocksDB, TronDatabase — set
  WriteOptions.sync(storage.isDbSync()), so the flag applies to
  both engines (the RocksDB path included).
• transHistory.switch: explained that when "off",
  TransactionHistoryStore.put and TransactionRetStore.put
  silently drop new writes (BooleanUtils.toBoolean(switch) gate),
  which makes gettransactioninfobyid return empty for any
  transaction processed while the switch was off. Reads of
  pre-existing data are not gated. Default "on".
• dbSettings is RocksDB-only: added a leading sentence to
  "RocksDB Optimization Parameters" noting that the block is only
  consumed by RocksDbSettings.initCustomSettings (and from there
  by RocksDbDataSourceImpl). The LevelDB code path has its own
  per-db tuning via storage.properties[*] with different key
  names (blockSize, writeBufferSize, cacheSize, maxOpenFiles,
  compressionType) and never reads dbSettings.

Formatting:

• Normalized the inline-note prefix to **Note**: — the trailing
  10-hours note used the bare > Note: form (which also wrapped
  to the next line); now matches the bolded single-line style used
  by the arm64 note added in this PR.

Test plan

• Verified Arch.isArm64() gating in DbConvert.java
• Verified the two @Parameters indices and default values in
  DbConvert.java
• Verified db.sync consumers across LevelDbDataSourceImpl,
  db2/common/LevelDB, db2/common/RocksDB, TronDatabase
• Verified transHistory.switch gates put() in
  TransactionHistoryStore and TransactionRetStore, and that
  Wallet.getTransactionInfoById reads from both
• Verified dbSettings only flows into RocksDbSettings and
  RocksDbDataSourceImpl; LevelDB path uses
  StorageUtils.getOptionsByDbName / Storage.newDefaultDbOptions
  with separate key names
• Visual review of the rendered page