feat(audit): /logs page — view + download recent audit log files

Adds a Streamlit page at ``/logs`` listing every
``datatools-*.jsonl`` file in ``audit_log_dir()`` (7-day window
per the retention sweep in b3ae913). Each entry shows filename,
mtime, byte size, and a ``st.download_button``. Today's file
gets its own section at the top.

The page also surfaces both paths as copyable monospace text:
the active log path (so users can grep/cat it directly on their
machine) and the folder path (so they can paste into Explorer /
Finder).

Wired into navigation via ``st.Page("pages/_Logs.py", ...)`` with
``url_path="logs"``. The sidebar entry is hidden by the same
``hide_streamlit_chrome`` CSS rule that hides ``/activate`` and
``/close`` — same pattern, same ``:has()`` + plain-fallback
selectors so the LinkContainer collapses cleanly in modern
browsers and the anchor is at least un-clickable in older ones.

License gate is OFF for this page (``gate_license=False``) — if a
user's license expires they may need logs to file a support
request; locking them out of their own audit history would be
hostile.

Next commit will wire the popover link.

Rollback: ``git revert HEAD`` removes the page and its nav entry;
the audit log itself keeps working.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

src/gui/components/_legacy.py

@@ -79,6 +79,8 @@ footer {
    container's spacing would still occupy a row. */
 [data-testid="stSidebarNav"] [data-testid="stSidebarNavLinkContainer"]:has(a[href$="/activate"]),
 [data-testid="stSidebarNav"] [data-testid="stSidebarNavLinkContainer"]:has(a[href$="/activate/"]),
+[data-testid="stSidebarNav"] [data-testid="stSidebarNavLinkContainer"]:has(a[href$="/logs"]),
+[data-testid="stSidebarNav"] [data-testid="stSidebarNavLinkContainer"]:has(a[href$="/logs/"]),
 [data-testid="stSidebarNav"] [data-testid="stSidebarNavLinkContainer"]:has(a[href$="/close"]),
 [data-testid="stSidebarNav"] [data-testid="stSidebarNavLinkContainer"]:has(a[href$="/close/"]) {
     display: none !important;
@@ -87,6 +89,8 @@ footer {
    least hide the anchor itself so the entry isn't clickable. */
 [data-testid="stSidebarNav"] a[href$="/activate"],
 [data-testid="stSidebarNav"] a[href$="/activate/"],
+[data-testid="stSidebarNav"] a[href$="/logs"],
+[data-testid="stSidebarNav"] a[href$="/logs/"],
 [data-testid="stSidebarNav"] a[href$="/close"],
 [data-testid="stSidebarNav"] a[href$="/close/"] {
     display: none !important;