fix(update): skip redundant daily download on weekly day

[tgies]

Summary

• When applying a fresh weekly snapshot, skip downloading the daily file for the same weekday (typically Sunday)
• That daily's data is already contained in the weekly, so downloading it was a no-op that wasted time and IO
• The daily-chain-only path (no new weekly) is unaffected — all 7 dailies are still checked

Fixes #5

Changes

• Added skip_weekday: Option<Weekday> parameter to build_daily_chain
• apply_weekly_then_dailies passes the weekly's weekday to skip
• run_update (daily-only path) passes None to check all dailies
• Added 6 unit tests covering date parsing and weekday skip logic

Test plan

• Unit tests for parse_fcc_date (standard, various months, invalid)
• Unit tests for weekday skip filtering (skip one, skip none)
• Unit test for Weekday::for_date matching
• Full test suite passes (372 tests, 0 failures)
• Clippy clean with -D warnings

[codecov]

Codecov Report

❌ Patch coverage is 78.78788% with 14 lines in your changes missing coverage. Please review.
✅ Project coverage is 85.17%. Comparing base (0897662) to head (30a5507).

Files with missing lines	Patch %	Lines
crates/uls-cli/src/commands/update.rs	78.78%	14 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main      #17      +/-   ##
==========================================
+ Coverage   84.95%   85.17%   +0.21%     
==========================================
  Files          57       57              
  Lines        9805     9867      +62     
==========================================
+ Hits         8330     8404      +74     
+ Misses       1475     1463      -12     

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