Milestone 2: persistent blob store, add/materialize/gc

iroh-blobs 0.35 fs store under <store_dir>/blobs. Add imports files or
whole directory trees (as Collections, deterministic order), Materialize
exports them with a real FICLONE reflink attempt and streaming-copy
fallback, Gc is an explicit mark-and-sweep rooted at the pins. Pins,
trusted peers and hash formats persist in meta.json (atomic writes).
Store reads run on a LocalPool because iroh-blobs entry readers are not
Send. Integration tests drive the real daemon binary: directory round
trip byte-identical, gc keeps pinned/drops unpinned, reflink verified on
the repo's own filesystem (XFS), plus a 32-case proptest round trip.

Dependencies: iroh-blobs =0.35.0 (the store itself; pinned per spec),
iroh-io (AsyncSliceReader traits to read store entries), reflink-copy
(FICLONE with copy fallback, per spec), proptest (dev-only, round-trip
property test).

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>

varde-daemon/Cargo.toml

@@ -13,6 +13,9 @@ path = "src/main.rs"
 
 [dependencies]
 varde-proto = { workspace = true }
+iroh-blobs = { workspace = true }
+iroh-io = { workspace = true }
+reflink-copy = { workspace = true }
 anyhow = { workspace = true }
 serde = { workspace = true }
 serde_json = { workspace = true }
@@ -24,3 +27,4 @@ tracing-subscriber = { workspace = true }
 
 [dev-dependencies]
 tempfile = "3"
+proptest = "1"