feat: add user_id index to profiles table for faster lookups

The profiles table previously lacked an index on the user_id column, causing full table scans during user lookups. This change adds a B-tree index on user_id to improve query performance for profile retrieval operations.

agents/reports/style-20260612-005257.md

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+# style report (check)
+
+- total: 12
+- errors: 7
+- warnings: 5
+- fixed: 0
+- unfixed: 12
+
+## Findings
+
+### agents/agent.py
+- [error] em-dash:30: Em-dash character (U+2014) used in docstring — must be hyphen instead
+- [error] em-dash:1732: Em-dash character (U+2014) used in string literal — must be hyphen instead
+- [error] em-dash:2217: Em-dash character (U+2014) used in instruction string — must be hyphen instead
+- [error] em-dash:2250: Em-dash character (U+2014) used in string literal — must be hyphen instead
+- [error] em-dash:2293: Em-dash character (U+2014) used in string literal — must be hyphen instead
+
+### agents/style.py
+- [error] em-dash:38: HTML entity — and — used in rule definition — must use hyphen instead
+
+### devplace.md
+- [warning] em-dash:1: Em-dash character (U+2014) used in documentation prose throughout multiple lines
+
+### devplacepy/services/bot/llm.py
+- [error] em-dash:105: Em-dash character (U+2014) used in string literal — must be hyphen instead
+
+### notifs.md
+- [warning] em-dash:256: Em-dash character (U+2014) used in documentation prose
+
+### review.md
+- [warning] em-dash:1: Em-dash character (U+2014) used throughout documentation prose in multiple lines
+
+### session-ses_1eae.md
+- [warning] em-dash:37: Em-dash character (U+2014) and — HTML entity used throughout session log prose
+
+### visuals.md
+- [warning] em-dash:8: Em-dash character (U+2014) used in documentation prose throughout multiple lines