…to prevent injection (#3219)

## Summary

This PR fixes identifier-injection vulnerabilities in three built-in
tools that interpolate caller-supplied parameters directly into SQL
without sanitisation.

---

### 1. `clickhouse-list-tables` — database identifier injection
(original fix)

`Tool.Invoke` interpolates the caller-supplied `database` parameter
directly into a `SHOW TABLES FROM %s` statement:

```go
query := fmt.Sprintf("SHOW TABLES FROM %s", database)
```

The existing comment acknowledges the risk. The fix adds a
`validIdentifier` regex (`^[A-Za-z_][A-Za-z0-9_]*$`) that must match
before interpolation.

Concrete payloads on a default ClickHouse deployment:

| `database` parameter | rendered query | effect |
|---|---|---|
| `default LIKE '%secret%'` | `SHOW TABLES FROM default LIKE '%secret%'`
| filters listing by attacker-chosen pattern |
| `system FORMAT JSONEachRow` | `SHOW TABLES FROM system FORMAT
JSONEachRow` | enumerates `system.*` (system.users, etc.) |
| `default INTO OUTFILE '/tmp/x.tsv'` | `SHOW TABLES FROM default INTO
OUTFILE '/tmp/x.tsv'` | writes to disk on ClickHouse host |

---

### 2. `bigquery-forecast` — backtick + column-name injection

Two injection classes:

**a. Backtick injection in `history_data` (table identifier path)**

```go
historyDataSource = fmt.Sprintf("TABLE `%s`", historyData)
```

When `allowed_datasets` is not configured (the default), no validation
runs before this line. An attacker-supplied `history_data` containing a
backtick closes the opening delimiter and appends arbitrary SQL:

```
history_data = "ds.tbl` UNION ALL SELECT secret FROM private.pii --"
→  TABLE `ds.tbl` UNION ALL SELECT secret FROM private.pii --`
```

**b. Column-name injection in `data_col`, `timestamp_col`, `id_cols`**

```go
sql := fmt.Sprintf(`... data_col => '%s', timestamp_col => '%s' ...`, dataCol, timestampCol, ...)
```

Column names are interpolated as single-quoted strings with no
validation. A value containing `'` breaks out of the string literal
context.

**Fix:** `ValidTableID` (restricts `history_data` to `[a-zA-Z0-9_]+`
components with 1–2 dots) applied in the table-ID else-branch;
`ValidColumnName` (`^[a-zA-Z_][a-zA-Z0-9_]*$`) applied to `data_col`,
`timestamp_col`, and each element of `id_cols`.

---

### 3. `bigquery-analyze-contribution` — backtick + OPTIONS injection

**a. Backtick injection in `input_data` (table identifier path)**

```go
inputDataSource = fmt.Sprintf("SELECT * FROM `%s`", inputData)
```

Same root cause as bigquery-forecast: when `allowed_datasets` is absent,
no validation before interpolation.

**b. Column-name and OPTIONS injection**

```go
options = append(options, fmt.Sprintf("IS_TEST_COL = '%s'", paramsMap["is_test_col"]))
// and each element of dimension_id_cols:
strCols = append(strCols, fmt.Sprintf("'%s'", c))
```

`is_test_col` and `dimension_id_cols` are column names interpolated into
BigQuery ML `OPTIONS()` string literals without validation.

`contribution_metric` (e.g. `SUM(col)/COUNT(DISTINCT col2)`) goes into
`OPTIONS(CONTRIBUTION_METRIC = '%s')`. A single-quote in this value
breaks the OPTIONS string literal.

**Fix:** `ValidTableID` for `input_data` in the table-ID else-branch;
`ValidColumnName` for `is_test_col` and each `dimension_id_cols`
element; single-quote check for `contribution_metric`.

---

## Shared validators in `bigquerycommon`

`ValidTableID` and `ValidColumnName` are exported from the
`bigquerycommon` package so both tools share the same rules. Tests are
in `validators_test.go`.

## Test plan

- [x] `go build ./...` clean
- [x] `go test ./internal/tools/bigquery/... -v` passes (all existing
tests + new `TestValidTableID`, `TestValidColumnName`)
- [x] `go test ./internal/tools/clickhouse/clickhouselisttables/... -v`
passes

## Not a dupe of #2811 / #779

Those cover the `templateParameter` flow
(`internal/util/parameters/parameters.go:applyEscape`). The three tools
fixed here use hard-coded `fmt.Sprintf` interpolation in their own
`Invoke` methods — none of the templateParameter mitigations apply.

---------

Co-authored-by: Yuan Teoh <45984206+Yuan325@users.noreply.github.com>