feat: job history view with filters, duration, and CSV export

[eclectic-coding]

Summary

• Adds GET /history — paginated list of all finished jobs (finished_at IS NOT NULL) with class name, queue, duration, and finished-at columns
• Filters: queue (click a badge to filter), class substring (?q=), and time period (1h / 24h / 7d / all)
• format_duration helper formats seconds as 45s / 2m 15s / 1h 3m
• CSV export (GET /history.csv) with id, class_name, queue_name, duration_seconds, finished_at — respects active filters
• "History" link added to queue subnav; current_section updated to include history and scheduled_jobs
• Controller refactored to before_action :set_filters + private filtered_scope — same pattern as JobsController
• Dev seeds updated with 8 finished jobs spanning 20 min → 8 days to exercise all period filter windows

Test plan

• GET /history — 200, page title, lists finished jobs, empty state, duration and columns
• GET /history?period= — filters correctly, ignores invalid values
• GET /history?queue= — filters by queue, shows active filter label with clear link
• GET /history?q= — class name substring filter
• GET /history.csv — attachment, correct headers, one row per job with duration_seconds
• Full suite: 135 examples, 0 failures, lint clean

🤖 Generated with Claude Code

[codecov-commenter]

Codecov Report

❌ Patch coverage is 93.54839% with 2 lines in your changes missing coverage. Please review.
✅ Project coverage is 97.90%. Comparing base (ca40995) to head (c3c484f).

Files with missing lines	Patch %	Lines
app/helpers/solid_stack_web/application_helper.rb	60.00%	2 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main      #14      +/-   ##
==========================================
- Coverage   98.44%   97.90%   -0.54%     
==========================================
  Files          16       17       +1     
  Lines         257      287      +30     
==========================================
+ Hits          253      281      +28     
- Misses          4        6       +2     

Files with missing lines	Coverage Δ
...trollers/solid_stack_web/application_controller.rb	85.18% <100.00%> (ø)
.../controllers/solid_stack_web/history_controller.rb	100.00% <100.00%> (ø)
app/helpers/solid_stack_web/application_helper.rb	81.81% <60.00%> (-18.19%)	⬇️

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