feat(search): add gpu-search command to find GPU instance types (#280)

* feat(search): add gpu-search command to find GPU instance types

Add `brev search` command (aliases: gpu-search, gpu, gpus) to search and
filter available GPU instance types across cloud providers.

Features:
- Filter by GPU name, provider, VRAM, compute capability, disk, boot time
- Sort by price, vram, boot-time, etc.
- Show instance features (stoppable, rebootable, flex-ports)
- JSON output support for scripting
- Pipeable output for chaining with other commands

Examples:
  brev search --gpu-name A100 --sort price
  brev search --min-vram 40 --max-boot-time 5
  brev search --json | jq '.[] | select(.price < 2)'

* refactor(search): address PR review feedback

- Add validation for --sort flag with clear error message for invalid options
- Extract common formatInstanceFields helper to reduce code duplication
- Move regex compilation to package level (compiled once, not per call)
- Replace magic number 730 with hoursInMonth constant
- Move public API URL to config.go as GetBrevPublicAPIURL()
- Use NewRestyClient instead of resty.New() for consistency

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

* fix(search): fix lint issues in gpu-search refactor

- Fix gofumpt formatting (var block alignment, struct field alignment)
- Reduce cyclomatic complexity in RunGPUSearch by extracting
  validateSortOption, displayEmptyResults, setTargetDisks, and
  displayResults helpers

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

---------

Co-authored-by: Claude Opus 4.5 <noreply@anthropic.com>

Author: theFong

pkg/cmd/cmd.go

@@ -14,6 +14,7 @@ import (
 	"github.com/brevdev/brev-cli/pkg/cmd/delete"
 	"github.com/brevdev/brev-cli/pkg/cmd/envvars"
 	"github.com/brevdev/brev-cli/pkg/cmd/fu"
+	"github.com/brevdev/brev-cli/pkg/cmd/gpusearch"
 	"github.com/brevdev/brev-cli/pkg/cmd/healthcheck"
 	"github.com/brevdev/brev-cli/pkg/cmd/hello"
 	"github.com/brevdev/brev-cli/pkg/cmd/importideconfig"
@@ -270,6 +271,7 @@ func createCmdTree(cmd *cobra.Command, t *terminal.Terminal, loginCmdStore *stor
 	}
 	cmd.AddCommand(workspacegroups.NewCmdWorkspaceGroups(t, loginCmdStore))
 	cmd.AddCommand(scale.NewCmdScale(t, noLoginCmdStore))
+	cmd.AddCommand(gpusearch.NewCmdGPUSearch(t, noLoginCmdStore))
 	cmd.AddCommand(configureenvvars.NewCmdConfigureEnvVars(t, loginCmdStore))
 	cmd.AddCommand(importideconfig.NewCmdImportIDEConfig(t, noLoginCmdStore))
 	cmd.AddCommand(shell.NewCmdShell(t, loginCmdStore, noLoginCmdStore))