Initial project skeleton (M0)

Add SPECS.md, JSON config loader with env overrides and validation,
and an empty tview shell with tabs and status bar.

Co-Authored-By: Claude Sonnet 5.5 <noreply@anthropic.com>

go.mod

@@ -0,0 +1,17 @@
+module git.stinnesbeck.com/nils/arr-tui
+
+go 1.26.8
+
+require (
+	github.com/gdamore/tcell/v2 v2.13.10
+	github.com/rivo/tview v0.42.0
+)
+
+require (
+	github.com/gdamore/encoding v1.0.1 // indirect
+	github.com/lucasb-eyer/go-colorful v1.3.0 // indirect
+	github.com/rivo/uniseg v0.4.7 // indirect
+	golang.org/x/sys v0.38.0 // indirect
+	golang.org/x/term v0.37.0 // indirect
+	golang.org/x/text v0.31.0 // indirect
+)