fix: harden exception handling, break ARC cycles, sync license/client

Replace bare except: with CatchableError across storage, query, Raft,
backup, and protocol code so Defects are not swallowed. Break uncollectable
ARC cycles in server shard/gossip callbacks via Server-owned refs and
cursor locals. Align package license with LICENSE (BSD-3-Clause), sync
README version, and point test_all at the canonical clients/nim baradb
client (parseConnectionString + aliases).

src/barabadb/core/httpserver.nim

@@ -103,7 +103,7 @@ proc verifyToken*(server: HttpServer, tokenStr: string): (bool, string, string)
     let userId = token.claims["sub"].node.str
     let role = if "role" in token.claims: token.claims["role"].node.str else: "user"
     return (true, userId, role)
-  except:
+  except CatchableError:
     return (false, "", "")
 
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