* feat(popup): show subscription renewal and expiration dates

Normalize official usage subscription dates separately from quota resets,
validate ISO calendar/clock values, and preserve true date-only semantics.
Render regional plan dates without inferring billing information from quotas.
Hide subscription enrichment in privacy mode and retained quota snapshots,
keep useful dates in quota-empty responses, and preserve account projections.

Documentation impact: update Unreleased, usage and development guidance;
remove only the completed subscription dates TODO. Preserve pinned Linux
0.73.0/0.74.0 emitted evidence and the source-only date-flag limitation.
Update all five catalogs and regenerate POT. Setup/defaults are unchanged,
so README remains valid; no new maintained document requires indexing.

Verification: make -k check completes with only the existing nine-provider
icon mapping failure, owned by the parallel provider update. QML has 2485
passes, 0 failures, 108 optional KDE skips; Python runs 374 tests with 1
optional KDE skip and no failures. Plasma import/type checks are partial;
the optional TODO gate skips because local main is unavailable.
Focused subscription QtTests pass 45 cases in UTC, Rome and Los Angeles.
make package and synthetic xvfb smoke pass, including Italian rendering,
privacy, failed-refresh retention, quota-empty usage and cached accounts.

* feat(providers): complete 0.74.0 metadata and setup

* fix(popup): preserve calendar dates across skipped civil days