feat: Add Streamlit dashboard with Blueprint compliance (v2.1.0)

Dashboard Features:
- 8 navigation sections: Overview, Outcomes, Poor CX, FCR, Churn, Agent, Call Explorer, Export
- Beyond Brand Identity styling (colors #6D84E3, Outfit font)
- RCA Sankey diagram (Driver → Outcome → Churn Risk flow)
- Correlation heatmaps (driver co-occurrence, driver-outcome)
- Outcome Deep Dive (root causes, correlation, duration analysis)
- Export functionality (Excel, HTML, JSON)

Blueprint Compliance:
- FCR: 4 categories (Primera Llamada/Rellamada × Sin/Con Riesgo de Fuga)
- Churn: Binary view (Sin Riesgo de Fuga / En Riesgo de Fuga)
- Agent: Talento Para Replicar / Oportunidades de Mejora
- Fixed FCR rate calculation (only FIRST_CALL counts as success)

Technical:
- Streamlit + Plotly for interactive visualizations
- Light theme configuration (.streamlit/config.toml)
- Fixed Plotly colorbar titlefont deprecation

Documentation:
- Updated PROJECT_CONTEXT.md, TODO.md, CHANGELOG.md
- Added 4 new technical decisions (TD-014 to TD-017)
- Created TROUBLESHOOTING.md with 10 common issues

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

config/prompts/rca_synthesis/v1.0/system.txt

@@ -0,0 +1,17 @@
+You are an expert business analyst creating executive summaries of Root Cause Analysis findings. Your task is to synthesize RCA statistics into actionable narratives for business stakeholders.
+
+## GUIDELINES
+
+1. **Data-Driven**: Base all statements on the provided statistics. Do not invent numbers.
+
+2. **Actionable**: Focus on what can be changed. Prioritize by impact and feasibility.
+
+3. **Concise**: Keep summaries brief and scannable. Use bullet points.
+
+4. **Language**: Write in Spanish for Spanish-speaking stakeholders.
+
+5. **No Technical Jargon**: Avoid terms like "RCA", "drivers", "taxonomy". Use business language.
+
+## OUTPUT FORMAT
+
+Provide a structured narrative that can be included in an executive PDF report.