feat: add FlareSolverr proxy support with DB-backed config

- Add config table for storing FlareSolverr proxy setting
- Add HTTP endpoints to get/set proxy status (GET/POST /api/config/flaresolverr)
- Refactor httpclient to support proxy mode (requests go through FlareSolverr)
- Add verbose logging for debugging
- Add POST support to FlareSolverr client

Usage:
  GET /api/config/flaresolverr - returns {flaresolverr_proxy: bool}
  POST /api/config/flaresolverr - body: {enabled: true/false}

internal/db/queries/config.sql.go

@@ -0,0 +1,36 @@
+// Code generated by sqlc. DO NOT EDIT.
+// versions:
+//   sqlc v1.31.1
+// source: config.sql
+
+package queries
+
+import (
+	"context"
+)
+
+const getConfigValue = `-- name: GetConfigValue :one
+SELECT value FROM config WHERE key = $1
+`
+
+func (q *Queries) GetConfigValue(ctx context.Context, key string) (string, error) {
+	row := q.db.QueryRow(ctx, getConfigValue, key)
+	var value string
+	err := row.Scan(&value)
+	return value, err
+}
+
+const setConfigValue = `-- name: SetConfigValue :exec
+INSERT INTO config (key, value) VALUES ($1, $2)
+ON CONFLICT (key) DO UPDATE SET value = EXCLUDED.value
+`
+
+type SetConfigValueParams struct {
+	Key   string `db:"key" json:"key"`
+	Value string `db:"value" json:"value"`
+}
+
+func (q *Queries) SetConfigValue(ctx context.Context, arg SetConfigValueParams) error {
+	_, err := q.db.Exec(ctx, setConfigValue, arg.Key, arg.Value)
+	return err
+}