feat: HTTP server for exporting Arborix bundles

Introduces a read-only HTTP server (WAI/Warp) backed by the content
store, exposing three bundle-export endpoints:

- GET /bundle/name/:name   — export by stored term name
- GET /bundle/hash/:hash   — export by full Merkle hash
- GET /terms               — plain-text listing (debug)

Also adds `tricu server` (aka `--serve`) CLI mode, move `resolveExportTarget` /
 `namesForHash` / `looksLikeHash` out of `Main.hs` into `ContentStore.hs`,
and cleans up unused exports and imports across `FileEval.hs` and `Wire.hs`.

src/Wire.hs

@@ -44,7 +44,7 @@ import Data.Foldable (traverse_)
 import Data.Map (Map)
 import Data.Text (Text, unpack)
 import Data.Text.Encoding (decodeUtf8, encodeUtf8)
-import Data.Word (Word16, Word32, Word64, Word8)
+import Data.Word (Word16, Word32, Word64)
 import Database.SQLite.Simple (Connection)
 import GHC.Generics (Generic)