Refactor Dolt repository requirement checks to be command and context-aware

The current implementation uses a static list to determine which commands require a valid Dolt repository. This approach is incorrect because repository requirements depend on both the subcommand being executed and whether the command is running locally or connecting to a remote host.

For example, `dolt backup sync` requires a local repository, while `dolt backup restore` does not. Similarly, `dolt init` should only run locally and never over a remote connection, while `dolt sql` can run in both contexts.

The static list approach forces overly broad decisions that apply to all subcommands of a command, when the requirement should be determined dynamically.

```go
// Current
commandsNotRequiringRepo := map[string]bool{
"init": true,
"sql": true,
"sql-server": true,
"backup": true, // Too broad - depends on subcommand
}
```

```go
// Proposal
type RepoNotRequiredCommand interface {
// RequiresRepo returns whether the command requires a valid repository
// based on the subcommand and connection context.
RequiresRepo(subcommand string, isRemoteConnection bool) bool
}
```

Start by locating the static commandsNotRequiringRepo map and the command-dispatch logic that uses it. Trace how backup subcommands, init, and sql determine local versus remote execution, then replace the broad checks with command- and context-aware behavior and verify the examples in the issue.

Written by the indexing model from the issue text.