feat: reword phase to epic, update mkdocs

docs/content/adr/0007-project-directory-structure.md

@@ -29,11 +29,11 @@ goplt/
 │   ├── config/            # ConfigProvider interface
 │   ├── logger/            # Logger interface
 │   ├── module/            # IModule interface
-│   ├── auth/              # Auth interfaces (Phase 2)
-│   ├── perm/              # Permission DSL (Phase 2)
+│   ├── auth/              # Auth interfaces (Epic 2)
+│   ├── perm/              # Permission DSL (Epic 2)
 │   └── infra/             # Infrastructure interfaces
 ├── modules/               # Feature modules
-│   └── blog/              # Sample module (Phase 4)
+│   └── blog/              # Sample module (Epic 4)
 ├── config/                # Configuration files
 │   ├── default.yaml
 │   ├── development.yaml
@@ -75,7 +75,7 @@ goplt/
 
 ### Implementation Notes
 - Initialize with `go mod init git.dcentral.systems/toolz/goplt`
-- Create all directories upfront in Phase 0
+- Create all directories upfront in Epic 0
 - Document structure in `README.md`
 - Enforce boundaries via `internal/` package visibility
 - Use `go build ./...` to verify structure