Implement structured logging with slog

- Replace zerolog with Go's standard slog package
- Add ColorHandler for terminal color output
- Add context-aware logging system
- Format attributes on the same line as log messages
- Use green color for INFO level logs
- Set up context value extraction helpers

🤖 Generated with [Claude Code](https://claude.ai/code)

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

misc/sql/initdb.sql

@@ -0,0 +1,43 @@
+DROP TABLE IF EXISTS snapshots;
+DROP TABLE IF EXISTS urls;
+
+CREATE TABLE urls (
+    id SERIAL PRIMARY KEY,
+    url TEXT NOT NULL,
+    host TEXT NOT NULL,
+    timestamp TIMESTAMP WITH TIME ZONE NOT NULL DEFAULT CURRENT_TIMESTAMP,
+    being_processed BOOLEAN
+);
+
+CREATE UNIQUE INDEX urls_url_key ON urls (url);
+CREATE INDEX idx_urls_url ON urls (url);
+CREATE INDEX idx_urls_timestamp ON urls (timestamp);
+CREATE INDEX idx_being_processed ON urls (being_processed);
+
+CREATE TABLE snapshots (
+    id SERIAL PRIMARY KEY,
+    url TEXT NOT NULL,
+    host TEXT NOT NULL,
+    timestamp TIMESTAMP WITH TIME ZONE NOT NULL DEFAULT CURRENT_TIMESTAMP,
+    mimetype TEXT,
+    data BYTEA,
+    gemtext TEXT,
+    links JSONB,
+    lang TEXT,
+    response_code INTEGER,
+    error TEXT,
+    header TEXT
+);
+
+CREATE UNIQUE INDEX idx_url_timestamp ON snapshots (url, timestamp);
+CREATE INDEX idx_url ON snapshots (url);
+CREATE INDEX idx_timestamp ON snapshots (timestamp);
+CREATE INDEX idx_mimetype ON snapshots (mimetype);
+CREATE INDEX idx_lang ON snapshots (lang);
+CREATE INDEX idx_response_code ON snapshots (response_code);
+CREATE INDEX idx_error ON snapshots (error);
+CREATE INDEX idx_host ON snapshots (host);
+CREATE INDEX idx_response_code_error ON snapshots (response_code, error);
+CREATE INDEX idx_response_code_error_nulls ON snapshots (response_code, error) WHERE response_code IS NULL AND error IS NULL;
+CREATE INDEX idx_snapshots_unprocessed ON snapshots (host) WHERE response_code IS NULL AND error IS NULL;
+CREATE INDEX idx_url_latest ON snapshots (url, timestamp DESC);