docs(data): write the data-layer docs in English

The three data modules' docs were in Italian, so the synchronization contract
added in the previous commit went in as Italian too, to match its file. English
is the project's language for docs, comments and READMEs alike, and a file half
in each is worse than either — so all three are translated, not just the new
section.

Content is otherwise unchanged, except the "synchronizations run on
commit/rollback" line in the two backend READMEs, which was vague before and is
now accurate about which hook sees the session/connection still bound, pointing
at flash-ext-data-core's README for the full contract.

Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>

flash-extensions/flash-ext-data-jdbc/docs/README.md

@@ -1,14 +1,15 @@
 # flash-ext-data-jdbc
 
-Backend JDBC per `flash-ext-data-core`.
+JDBC backend for `flash-ext-data-core`.
 
-## Scopo
+## Purpose
 
-Questo modulo implementa `TxManager` sopra `DataSource` e fornisce una base repository SQL raw.
+This module implements `TxManager` on top of a `DataSource` and provides a raw-SQL repository base
+class.
 
-## Come si usa
+## How to use it
 
-### 1. Creare il manager
+### 1. Create the manager
 
 ```java
 DataSource dataSource = ...;
@@ -16,11 +17,12 @@ JdbcTxManager txManager = new JdbcTxManager(dataSource);
 DataExtension extension = new DataExtension(txManager);
 ```
 
-### 2. Installare l’estensione in Flash
+### 2. Install the extension in Flash
 
-Come per Hibernate, `DataExtension` registra `Tx` nel `FlashContext` e abilita `@Transactional` sugli handler class-based.
+As with Hibernate, `DataExtension` registers `Tx` in the `FlashContext` and enables
+`@Transactional` on class-based handlers.
 
-### 3. Definire una repository
+### 3. Define a repository
 
 ```java
 public final class UserRepository extends JdbcRepository<User, Long> {
@@ -35,7 +37,7 @@ public final class UserRepository extends JdbcRepository<User, Long> {
 }
 ```
 
-Anche qui puoi esporre `Spec` riusabili e comporre query dal service layer:
+Here too you can expose reusable `Spec`s and compose queries from the service layer:
 
 ```java
 public final class UserRepository extends JdbcRepository<User, Long> {
@@ -47,7 +49,7 @@ public final class UserRepository extends JdbcRepository<User, Long> {
 }
 ```
 
-Per il salvataggio e l’update devi fornire il binding esplicito:
+Saving and updating need an explicit binding:
 
 ```java
 @Override
@@ -61,36 +63,39 @@ protected void bindInsert(PreparedStatement ps, User entity) throws SQLException
 }
 ```
 
-## Come funziona sotto
+## How it works underneath
 
-- La tx corrente espone una `Connection`.
-- `Tx.resource(Connection.class)` recupera la connessione bindata al thread.
-- `REQUIRES_NEW` sospende la connessione attiva e ne apre una nuova.
-- `NOT_SUPPORTED` sospende il contesto e prosegue senza tx.
+- The current transaction exposes a `Connection`.
+- `Tx.resource(Connection.class)` retrieves the connection bound to the thread.
+- `REQUIRES_NEW` suspends the active connection and opens a new one.
+- `NOT_SUPPORTED` suspends the context and continues without a transaction.
 
-## Repository base
+## Repository base class
 
-`JdbcRepository` fornisce:
+`JdbcRepository` provides:
 
-- query `select` con `queryOne`, `queryMany`
-- mutation con `mutate`
-- persistenza con `doSave`, `doUpdate`
-- paging con `doFindPage`
+- `select` queries through `queryOne`, `queryMany`
+- mutations through `mutate`
+- persistence through `doSave`, `doUpdate`
+- paging through `doFindPage`
 - bulk `deleteAll(Spec<T>)`
-- helper raw `queryOne(...)`, `queryMany(...)`, `mutate(...)`
+- raw helpers `queryOne(...)`, `queryMany(...)`, `mutate(...)`
 
-Le repository concrete devono solo tradurre tra `ResultSet` e dominio.
+Concrete repositories only have to translate between `ResultSet` and the domain.
 
-## Semantica transazionale
+## Transactional semantics
 
-- `REQUIRED`: join o apertura nuova tx.
-- `REQUIRES_NEW`: sospensione del contesto corrente.
-- `SUPPORTS`: join se c’è tx, altrimenti no-op.
-- `NOT_SUPPORTED`: sospende e prosegue senza tx.
-- `MANDATORY`: fallisce se non c’è tx.
+- `REQUIRED`: join, or open a new transaction.
+- `REQUIRES_NEW`: suspend the current context.
+- `SUPPORTS`: join if a transaction exists, otherwise no-op.
+- `NOT_SUPPORTED`: suspend and continue without a transaction.
+- `MANDATORY`: fail if there is no transaction.
 
-## Note
+## Notes
 
-- La `Connection` viene chiusa a fine tx nuova.
-- Le synchronizations vengono eseguite al commit/rollback.
-- Se una repository usa `doDelete(T)`, il comportamento predefinito è non supportato: usare `deleteById` o override specifico.
+- The `Connection` is closed when a new transaction ends.
+- Synchronizations registered in a transaction fire when *that* transaction completes:
+  `beforeCommit` while it is still active and the `Connection` still bound, the post-completion
+  hooks once it is unbound. See `flash-ext-data-core/docs/README.md` for the full contract.
+- If a repository uses `doDelete(T)`, the default behaviour is unsupported: use `deleteById` or
+  override it.