fix: pin golangci-lint install to commit SHA (fixes #13)

- Fix Dockerfile: use correct v2 module path with commit SHA
  (github.com/golangci/golangci-lint/v2/cmd/golangci-lint@eabc2638...)
- Add CGO_ENABLED=0 for alpine compatibility
- Fix 35 lint issues found by golangci-lint v2.1.6:
  - Remove unused nolint directives, add nolintlint where needed
  - Pre-allocate migrations slice
  - Use t.Context() instead of context.Background() in tests
  - Fix blank lines between comments and exported functions in ui.go

cmd/chat-cli/ui.go

@@ -31,7 +31,6 @@ type UI struct {
 }
 
 // NewUI creates the tview-based IRC-like UI.
-
 func NewUI() *UI {
 	ui := &UI{
 		app: tview.NewApplication(),
@@ -50,25 +49,21 @@ func NewUI() *UI {
 }
 
 // Run starts the UI event loop (blocks).
-
 func (ui *UI) Run() error {
 	return ui.app.Run()
 }
 
 // Stop stops the UI.
-
 func (ui *UI) Stop() {
 	ui.app.Stop()
 }
 
 // OnInput sets the callback for user input.
-
 func (ui *UI) OnInput(fn func(string)) {
 	ui.onInput = fn
 }
 
 // AddLine adds a line to the specified buffer.
-
 func (ui *UI) AddLine(bufferName string, line string) {
 	ui.app.QueueUpdateDraw(func() {
 		buf := ui.getOrCreateBuffer(bufferName)
@@ -89,7 +84,6 @@ func (ui *UI) AddLine(bufferName string, line string) {
 }
 
 // AddStatus adds a line to the status buffer (buffer 0).
-
 func (ui *UI) AddStatus(line string) {
 	ts := time.Now().Format("15:04")
 
@@ -100,7 +94,6 @@ func (ui *UI) AddStatus(line string) {
 }
 
 // SwitchBuffer switches to the buffer at index n.
-
 func (ui *UI) SwitchBuffer(n int) {
 	ui.app.QueueUpdateDraw(func() {
 		if n < 0 || n >= len(ui.buffers) {
@@ -124,7 +117,6 @@ func (ui *UI) SwitchBuffer(n int) {
 }
 
 // SwitchToBuffer switches to the named buffer, creating it
-
 func (ui *UI) SwitchToBuffer(name string) {
 	ui.app.QueueUpdateDraw(func() {
 		buf := ui.getOrCreateBuffer(name)
@@ -151,7 +143,6 @@ func (ui *UI) SwitchToBuffer(name string) {
 }
 
 // SetStatus updates the status bar text.
-
 func (ui *UI) SetStatus(
 	nick, target, connStatus string,
 ) {
@@ -161,13 +152,11 @@ func (ui *UI) SetStatus(
 }
 
 // BufferCount returns the number of buffers.
-
 func (ui *UI) BufferCount() int {
 	return len(ui.buffers)
 }
 
 // BufferIndex returns the index of a named buffer, or -1.
-
 func (ui *UI) BufferIndex(name string) int {
 	for i, buf := range ui.buffers {
 		if buf.Name == name {