feat(sources): upload tarball/zipfile archives as sources — unpack, scan, and replace in place

Phase 49 (owner request, chat 2026-08-28: "The git sources page should
remove local directory and should instead accept a tarball or zipfile
upload which it will unpack and scan … reuploading the same tarball
should not create a new folder, but should unpack and overwrite the
previously unpacked content" — design confirmed in the same
conversation):

* POST /api/git-sources/upload (admin-only, require_admin): accepts
  .tar/.tar.gz/.tgz/.zip, streams it with the BOR_UPLOAD_MAX_MB cap
  (bounds BOTH the compressed upload and the total extracted bytes —
  zip-bomb guard), safely unpacks (absolute/traversal/symlink/hardlink
  escape and device/FIFO members rejected), and atomically swaps the
  content in over BOR_UPLOAD_DIR/<name>/ (name = filename minus the
  archive suffix — no missing window, a failed upload never touches the
  existing folder/row/KB). The git_sources row is upserted by path
  (kind='local', no duplicates, added_at preserved), the models are
  checked fail-fast (503 sanitized when down — the folder/row stay
  committed and the next sync/re-upload retries idempotently), and the
  source is scanned synchronously in the request (single-source
  import_sources prune=True + change-gated KB overview), answering 200
  with the sync-style counts. One upload at a time (409); the request
  session is released before the scan so a concurrent TRUNCATE cannot
  deadlock against it.
* app/rag/archive_upload.py: ArchiveUploadError, ARCHIVE_SUFFIXES,
  archive_source_name (safe-name derivation), unpack_archive (guarded
  zip/tar extraction with the extracted-byte cap, no partial state),
  swap_in (atomic replace with restore-on-failure) — fully unit-tested.
* app/config.py + .env.example: BOR_UPLOAD_DIR (default
  ~/bor-sources/uploads, deliberately separate from the git checkouts)
  and BOR_UPLOAD_MAX_MB (default 512; a validator fails loud at
  startup on <= 0).
* python-multipart added to the dependencies — FastAPI's required
  multipart parser (an A2 implementation detail, phase locked decision).
* The Sources page: the phase-38 "Add a local directory" form is
  removed; #archive-upload-form takes its place (labeled file input,
  "Upload & scan" button, the §7.4 never-stale lifecycle, inline
  role=alert error, role=status count line); hint + table caption
  updated. The POST /api/git-sources kind=local API contract is
  UNCHANGED — a plain directory is still registrable via the API, and
  existing Local rows list/remove/sync exactly as before.
* The phase-38 story E2E (test_local_directory_sources.py) is rewritten
  API-driven — the form it drove is gone; its acceptance stands.
* The story E2E (test_archive_upload_sources.py): the swap,
  upload→scan→list (the deterministic "Uploading…" in-flight state, the
  Local row, /api/docs + the RAG catalog), same-filename re-upload
  (in-place replace, prune, no duplicate row, v2-only folder), the
  422 inline error + recovery (the form is not wedged), and the
  anonymous gate + 403.
* README: the archive-upload section (formats, naming rule, in-place
  replace, both new settings), the local-directory form removal noted,
  config reference rows for BOR_UPLOAD_DIR / BOR_UPLOAD_MAX_MB.

Gates: unit+integration green, app/ coverage 99%, the story E2E green
in isolation, the regression suites (git sources admin, local
directory sources, sync button, import documents, nav rename, smoke,
shared header) green in isolation, ruff + pyright clean.

Note: per this phase's file-level staging, frontend/assets/styles.css
also carries the small same-day in-flight owner rework already in the
working tree (the .sign-in-mobile companion rule for the phase-48
mobile sign-in copy); the phase-49 change is the upload form's block.

uv.lock

@@ -62,6 +62,7 @@ dependencies = [
     { name = "pydantic" },
     { name = "pydantic-settings" },
     { name = "python-dotenv" },
+    { name = "python-multipart" },
     { name = "sqlalchemy" },
     { name = "uvicorn", extra = ["standard"] },
 ]
@@ -88,6 +89,7 @@ requires-dist = [
     { name = "pydantic", specifier = ">=2.7,<3.0" },
     { name = "pydantic-settings", specifier = ">=2.3,<3.0" },
     { name = "python-dotenv", specifier = ">=1.0,<2.0" },
+    { name = "python-multipart", specifier = ">=0.0.9,<0.1" },
     { name = "sqlalchemy", specifier = ">=2.0,<2.1" },
     { name = "uvicorn", extras = ["standard"], specifier = ">=0.30,<1.0" },
 ]
@@ -896,6 +898,15 @@ wheels = [
     { url = "https://files.pythonhosted.org/packages/0d/17/c5c6b53ddc18f297992099b3d9ec16c855c0ccc83263a21fe4d1c625ec6c/python_dotenv-1.2.3-py3-none-any.whl", hash = "sha256:904552145e8bfed22162c09dab1c2b9b54fefa7b23ba780f4f26ca0316b0f0d9", size = 22780, upload-time = "2026-08-16T16:54:52.473Z" },
 ]
 
+[[package]]
+name = "python-multipart"
+version = "0.0.32"
+source = { registry = "https://pypi.org/simple" }
+sdist = { url = "https://files.pythonhosted.org/packages/5b/42/55c32bb9b12693c092ad250a0e82edb5b31ddeda6eb772de5f308b3804ad/python_multipart-0.0.32.tar.gz", hash = "sha256:be54b7f3fa167bb83e4fcd936b887b708f4e57fe75911c02aebf53efaf8d938e", size = 46881, upload-time = "2026-06-04T16:18:58.647Z" }
+wheels = [
+    { url = "https://files.pythonhosted.org/packages/e1/04/e8135ebd1ad02c56ec633277529b2602ff99ff634be76cdba5744cf554fd/python_multipart-0.0.32-py3-none-any.whl", hash = "sha256:ff6d3f776f16878c894e52e107296ffc890e913c611b1a4ec6c44e2821fe2e23", size = 30042, upload-time = "2026-06-04T16:18:57.319Z" },
+]
+
 [[package]]
 name = "pyyaml"
 version = "6.0.3"