feat(s3): add S3-compatible object storage connections

[perundio]

Summary

• Add native S3-compatible object storage connections for AWS S3, MinIO, and other SigV4-compatible endpoints across desktop and web.
• Finish the S3 browser with bucket management, folder/prefix creation, paginated object listing, upload/download/preview/delete, and copy/move/rename workflows.
• Harden the implementation for merge by moving temporary S3 session tokens into the existing secret/session lifecycle, fixing SigV4 path canonicalization for special-character keys, rebasing onto the latest main, and expanding targeted test coverage.

What’s Included

• Connection dialog support for endpoint, region, addressing style, optional session token, and read-only mode.
• Native S3 runtime integration in dbx-core, dbx-web, and Tauri commands.
• S3 browser UI with:
  • list/create/delete bucket
  • create folder/prefix
  • paginated ListObjectsV2 browsing with NextContinuationToken
  • upload, download, preview, delete object
  • copy, move, and rename object
• Updated S3 driver branding/icon.
• Secret-handling fixes so temporary S3 session tokens do not persist in plaintext when save_password = false.
• SigV4 fixes for already-escaped paths plus regression coverage for path-style and virtual-hosted URLs with spaces, Unicode, %, and ? in keys.

Test Plan

• cargo test -p dbx-core s3:: --lib
• cargo test -p dbx-core session_credentials::tests --lib
• pnpm typecheck
• pnpm vitest run apps/desktop/src/components/s3/__tests__/S3Browser.spec.ts
• Manual smoke test against local MinIO / AWS-compatible endpoint
  • connect using endpoint + credentials
  • create/delete bucket
  • create prefix, upload/download/preview/delete object
  • copy/move/rename object
  • browse paginated folders with 200+ entries
  • verify read-only mode blocks write operations

Notes For Review

• The PR head has been rebased onto the current main and the previous merge conflict state is resolved.
• The review-requested security and signing fixes are included in the latest head commit.

[github-actions]

🌐 I18n autofill completed

✅ Added translations for 33 new zh-CN i18n keys.

Locale	Added entries
es	33
it	33
ja	33
pt-BR	33
zh-TW	33

[t8y2]

I'm requesting changes for now. Three issues need fixing before this is safe to merge:

1. ConnectionDialog.vue stores the temporary S3 session token in external_config. The existing persistence, no-save-password, and cloud-sync scrubbers do not treat this field as a secret, so it can remain in plaintext configuration and shared runtime state. Please move it through the same secret-store/session-isolation lifecycle as the secret access key.

2. sigv4.rs passes the already escaped Url::path() through percent_encode_path again. Keys containing spaces, Unicode, %, ?, or similar characters are therefore signed with %25 escapes that differ from the transmitted path, causing SignatureDoesNotMatch. Canonicalize the raw key exactly once and add path-style and virtual-hosted regression tests with special-character keys.

   The url crate documents that Url::set_path percent-encodes its input, while AWS SigV4 requires the canonical URI to match the transmitted absolute path: https://docs.rs/url/2.5.8/url/struct.Url.html#method.set_path and https://docs.aws.amazon.com/IAM/latest/UserGuide/reference_sigv-create-signed-request.html

3. S3Browser.vue always requests 200 entries with a null continuation token and ignores isTruncated/nextContinuationToken, so larger folders silently hide every later object and common prefix. Add load-more or bounded page accumulation with a 201+ object/prefix test. AWS documents that truncated ListObjectsV2 results must continue with NextContinuationToken: https://docs.aws.amazon.com/AmazonS3/latest/API/API_ListObjectsV2.html#AmazonS3-ListObjectsV2-response-NextContinuationToken

GitHub also currently reports this head as conflicting, while the main CI workflow stopped at action_required without running any jobs.

[perundio]

Thanks for the detailed review and for calling out the risky parts so precisely.

I’ve addressed the requested changes in the latest head:

• moved the temporary S3 session token into the existing secret-store / session-isolation flow so it no longer stays in plaintext config when save_password = false
• fixed SigV4 canonical URI handling so already-escaped paths are signed exactly as transmitted, and added regression tests for path-style and virtual-hosted URLs with special-character keys
• updated S3Browser.vue to continue truncated ListObjectsV2 results via NextContinuationToken, and added a 201+ object/prefix UI test
• rebased the branch onto the latest main and resolved the previous conflict state

Also took the opportunity to finish the missing object-browser workflows in the same pass: bucket delete, folder/prefix creation, download, and copy/move/rename operations.

Thanks again for the careful review.