docs(setup-guide): add Report Output Controls guide

[prokopetsv]

Problem

There was no documentation explaining how to use filters, slices, sort, and row limits on reports. Users discovering the Output Controls panel had no reference for what each control does, how slices differ from filters (a non-obvious LEFT JOIN distinction), what operators are available per column type, or what causes the "Output controls validation failed" error.

Solution

Added a new guide at docs/getting-started/setup-guide/output-controls.md covering all four controls with step-by-step instructions, operator reference tables, behavioral notes, and 7 annotated screenshots. Registered the page in astro.config.mjs under Setup Guide, positioned after Joinable Data Marts (the prerequisite for slices). The guide was written to the skimmable-developer standard: short sentences, active voice, no filler, no nominalizations.

Changes

• Added docs/getting-started/setup-guide/output-controls.md covering Filters, Slices, Sort, Limit, Order of Execution, and schema-change behavior
• Documented that output controls work for both web app Data Marts and OWOX Extension reports
• Added step-by-step navigation path to the Output Controls panel (Destinations tab → three-dot menu → Edit report → Report Columns → sliders icon)
• Added operator reference table for all column types including Time (missing from original draft); corrected "relative date" label to match UI label "relative"
• Documented N bounds (1–3650) for Last N days / Last N months presets
• Documented AND-only filter logic and explicit absence of OR support
• Documented sort and slice column-selection validation constraint with guidance on the resulting error
• Added edit (pencil) and remove (×) guidance for filters, slices, and sort rules
• Added "Keep Rules Valid After Schema Changes" section with validation error screenshot
• Registered docs/getting-started/setup-guide/output-controls in astro.config.mjs sidebar after joinable-data-marts
• Added link to Extension Data Marts in Related Links