Add template support for issue creation (bd-164b)

- Built-in templates: epic, bug, feature (embedded in binary)
- Custom templates in .beads/templates/ (override built-ins)
- Commands: bd template list/show/create
- Flag: bd create --from-template <name> "Title"
- Template fields: description, type, priority, labels, design, acceptance
- Security: sanitize template names to prevent path traversal
- Flag precedence: explicit flags override template defaults
- Tests: template loading, security, flag precedence
- Docs: commands/template.md and README.md updated

Closes bd-164b

Amp-Thread-ID: https://ampcode.com/threads/T-118fe54f-b112-4f99-a3d9-b7df53fb7284
Co-authored-by: Amp <amp@ampcode.com>

internal/rpc/server_issues_epics.go

@@ -458,6 +458,8 @@ func (s *Server) handleReady(req *Request) Response {
 		Priority:   readyArgs.Priority,
 		Limit:      readyArgs.Limit,
 		SortPolicy: types.SortPolicy(readyArgs.SortPolicy),
+		Labels:     normalizeLabels(readyArgs.Labels),
+		LabelsAny:  normalizeLabels(readyArgs.LabelsAny),
 	}
 	if readyArgs.Assignee != "" {
 		wf.Assignee = &readyArgs.Assignee