Add Phase 2 optimizations: status API caching and improved Redis pipelining

- Add in-memory cache for /status endpoint with 30s TTL
- Cache keyed by view parameters to handle different query patterns
- Add cache clearing for tests to prevent interference
- Optimize get_queue_metrics to use single pipeline for all Redis calls
  - Previously made 7+ separate pipeline calls
  - Now combines all queue metrics into one pipeline (7n+2 operations)
  - Reduces Redis round trips and improves API response time
- Update unit tests to match new pipelining behavior
- All 866 tests passing

spec/integration/api/v3/status_spec.rb

@@ -17,6 +17,8 @@ describe Vmpooler::API::V3 do
   # https://rubydoc.info/gems/sinatra/Sinatra/Base#reset!-class_method 
   before(:each) do
     app.reset!
+    # Clear status cache to prevent test interference
+    Vmpooler::API::V3.clear_status_cache
   end
 
   describe 'status and metrics endpoints' do

spec/unit/api/helpers_spec.rb

@@ -125,8 +125,12 @@ describe Vmpooler::API::Helpers do
           {'name' => 'p2'}
       ]
 
-      allow(redis).to receive(:pipelined).with(no_args).and_return [1,1]
-      allow(redis).to receive(:get).and_return(1,0)
+      # Mock returns 7*2 + 2 = 16 results (7 queue types for 2 pools + 2 global counters)
+      # For each pool: [request, processing, odcreate, pending, ready, running, completed]
+      # Plus 2 global counters: clone (1), ondemandclone (0)
+      # Results array: [1,1, 1,1, 1,1, 1,1, 1,1, 1,1, 1,1, 1, 0]
+      #                [req,  proc,  odc,   pend, rdy,  run,  comp, clone, odc]
+      allow(redis).to receive(:pipelined).with(no_args).and_return [1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,0]
 
       expect(subject.get_queue_metrics(pools, redis)).to eq({requested: 6, pending: 2, cloning: 1, booting: 1, ready: 2, running: 2, completed: 2, total: 14})
     end
@@ -137,8 +141,8 @@ describe Vmpooler::API::Helpers do
           {'name' => 'p2'}
       ]
 
-      allow(redis).to receive(:pipelined).with(no_args).and_return [1,1]
-      allow(redis).to receive(:get).and_return(5,0)
+      # Mock returns 7*2 + 2 = 16 results with clone=5 to cause negative booting
+      allow(redis).to receive(:pipelined).with(no_args).and_return [1,1,1,1,1,1,1,1,1,1,1,1,1,1,5,0]
 
       expect(subject.get_queue_metrics(pools, redis)).to eq({requested: 6, pending: 2, cloning: 5, booting: 0, ready: 2, running: 2, completed: 2, total: 14})
     end