docs: fix 21 typos in comments and documentation

[Avicennasis]

Summary

Fix 21 typos in Go comments, doc comments and one error string across 7 files.

• utils/common.go: an existed dir -> an existing dir; an exist file -> an existing file; // Containe checks -> // Contain checks (doc comment now matches the real Contain func); automaticly -> automatically; signed data an a public key -> and a public key; decryptes -> decrypts
• models/dockerv2.go: //GetTags return tas data -> //GetTags returns tag data
• models/appv1.go: the Artifcat V1 object -> the Artifact V1 object
• handler/... (not touched)
• updateservice/client/appv1.go: comment checks if a protocal is -> checks if a protocol is (the protocal parameter and appV1Protocal const are left alone - renaming identifiers is out of scope)
• updateservice/storage/local.go: an UpdateServceStorage interface with a local implmentation -> an UpdateServiceStorage interface with a local implementation (doc comment now matches the real UpdateServiceStorage interface); namespace/repositoryi/os/arch/appname -> namespace/repository/os/arch/appname
• updateservice/snapshot/snapshot.go: plugin use after -> plugin uses after; 'appv1',calling -> 'appv1', calling; second one is group snapshot -> another is group snapshot; encrytped -> encrypted; TODO: Better structed -> TODO: Better structured
• cmd/daemon.go: deamon -> daemon in four comments

Two notes for reviewers:

1. One change touches a runtime string, not a comment. In updateservice/storage/local.go the error text "invalid key deteced in StorageLocal.List" becomes "invalid key detected in StorageLocal.List". The other six sibling errors in that same file already say detected, so this makes the set consistent. Nothing in the repo asserts on this string (grepped tests/), but please confirm no downstream log parsing depends on it.
2. cmd/daemon.go had a fourth deamon (in the monitorDaemon doc comment) that was not in the original report; it is fixed too, since leaving one misspelling of the same word in the same file would be arbitrary.

No identifiers were renamed and no behaviour changes: GetPackageRESTV1Hanfdler, DeletePacakgeRESTV1Handler, appV1Protocal, monitorDeamonCmd and startDeamon are all left exactly as they are, because their doc comments must keep matching the declared names.

Commit is DCO signed-off per the Contributing section of the README.