Stock prices rose today in what analysts described as a technical rebound from the market's free-fall slide of the past several weeks. The Dow Jones average of 30 industrials, down 173.02 points over the past three sessions, recovered 30.94 to 2,514.36 by 3 p.m. on Wall Street. Gainers outnumbered losers by about 8 to 7 in nationwide trading of New York Stock Exchange-listed issues, with 821 up, 720 down and 444 unchanged. Analysts said buyers were encouraged by hopes that the markets had gone too far in their appraisal of the potential calamities resulting from the showdown in the Middle East. But by near-unanimous agreement the mood in the marketplace remained cautious and touchy. It will take months, economists observe, to gauge the effects on business aactivity of the upsurge in oil prices and interest rates that followed Iraq's Aug. 2 invasion of Kuwait. Even without that disruptive influence, the domestic economy was widely believed to have been verging on a recession as it began the second half of 1990. Among actively traded blue chips, General Electric rose 1&lsqb; to 59|; International Business Machines 1&rsqb; to 98\; Boeing 2} to 45\, and American Telephone & Telegraph } to 31\. Federal National Mortgage gained 1} to 28&rsqb;. The stock traded as low as 24~ Thursday before the company announced that it had earmarked as much as $500 million for buybacks of its common shares and warrants. The NYSE's composite index of all its listed common stocks rose 1.07 to 169.95. At the American Stock Exchange, the market value index was down 1.14 at 314.71. Volume on the Big Board came to 169.08 million shares with an hour to go.