docs: add census documentation and final research report

- Add 37 census documentation files for IBGE census datasets (1970-2010)
- Add dataviz wordcloud scripts and images
- Add relatorio_final.md with research findings on households and living conditions

New data from DuckDB queries:
- 90.7M households, 203M population
- 53.2% Black population
- 27.9% female-headed households
- 46.6% urban sewage without collection/treatment
- 15,816 favela sectors (2010)
- 68% Black population in Fortaleza

docs/dataviz/wordcloud_datasets.py

@@ -0,0 +1,33 @@
+#!/usr/bin/env python3
+import json
+from collections import Counter
+from wordcloud import WordCloud
+import matplotlib.pyplot as plt
+
+with open('context/basedosdados-schema.json') as f:
+    schema = json.load(f)
+
+dataset_names = []
+for dataset in schema.keys():
+    parts = dataset.replace('br_', '').replace('mundo_', '').replace('eu_', '').split('_')
+    dataset_names.extend([p for p in parts if len(p) >= 3])
+
+word_freq = Counter(dataset_names)
+
+wc = WordCloud(
+    width=1600, 
+    height=800, 
+    background_color='white',
+    max_words=100,
+    colormap='plasma',
+    min_font_size=10
+).generate_from_frequencies(word_freq)
+
+plt.figure(figsize=(20, 10))
+plt.imshow(wc, interpolation='bilinear')
+plt.axis('off')
+plt.tight_layout(pad=0)
+plt.savefig('docs/wordcloud_datasets.png', dpi=150, bbox_inches='tight')
+print("Saved docs/wordcloud_datasets.png")
+print(f"Total unique words: {len(word_freq)}")
+print("Top 30:", word_freq.most_common(30))