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>

go.mod

@@ -7,28 +7,24 @@ toolchain go1.24.2
 require (
 	github.com/anthropics/anthropic-sdk-go v1.14.0
 	github.com/fatih/color v1.18.0
-	github.com/google/uuid v1.6.0
+	github.com/fsnotify/fsnotify v1.9.0
+	github.com/ncruces/go-sqlite3 v0.29.1
 	github.com/spf13/cobra v1.10.1
 	github.com/spf13/viper v1.21.0
 	golang.org/x/mod v0.29.0
 	golang.org/x/sys v0.36.0
 	gopkg.in/natefinch/lumberjack.v2 v2.2.1
-	modernc.org/sqlite v1.38.2
+	gopkg.in/yaml.v3 v3.0.1
 	rsc.io/script v0.0.2
 )
 
 require (
-	github.com/dustin/go-humanize v1.0.1 // indirect
-	github.com/fsnotify/fsnotify v1.9.0 // indirect
 	github.com/go-viper/mapstructure/v2 v2.4.0 // indirect
 	github.com/inconshreveable/mousetrap v1.1.0 // indirect
 	github.com/mattn/go-colorable v0.1.13 // indirect
 	github.com/mattn/go-isatty v0.0.20 // indirect
-	github.com/ncruces/go-sqlite3 v0.29.1 // indirect
-	github.com/ncruces/go-strftime v0.1.9 // indirect
 	github.com/ncruces/julianday v1.0.0 // indirect
 	github.com/pelletier/go-toml/v2 v2.2.4 // indirect
-	github.com/remyoudompheng/bigfft v0.0.0-20230129092748-24d4a6f8daec // indirect
 	github.com/sagikazarmark/locafero v0.11.0 // indirect
 	github.com/sourcegraph/conc v0.3.1-0.20240121214520-5f936abd7ae8 // indirect
 	github.com/spf13/afero v1.15.0 // indirect
@@ -41,10 +37,6 @@ require (
 	github.com/tidwall/pretty v1.2.1 // indirect
 	github.com/tidwall/sjson v1.2.5 // indirect
 	go.yaml.in/yaml/v3 v3.0.4 // indirect
-	golang.org/x/exp v0.0.0-20250620022241-b7579e27df2b // indirect
 	golang.org/x/text v0.29.0 // indirect
 	golang.org/x/tools v0.37.0 // indirect
-	modernc.org/libc v1.66.3 // indirect
-	modernc.org/mathutil v1.7.1 // indirect
-	modernc.org/memory v1.11.0 // indirect
 )