I believe I remember reading in WoR or the Supplemental that the Clan caches were empty of WarShips.
It is mentioned that the naval caches of some Clans (as to the Star Adders) are empty. But it is not mentioned that all naval caches have been depleted.
I think there might have been some left (maybe a dozen or so, and maybe some designs we do not have gotten Clan updates (a Farragut C and/or Soyal C would be very appreciated :) ).
While they lost the Ravens, the most powerful warship, the Leviathan Prime, was built by the Steel Vipers. They were not a very economic powerhorse, nevertheless they were capable to construct this super ship. If the Homeclans want to have such ships and an effective warship-building industry they will do this.
They will need time but time they have (60 years no contact to the Homeworlds in 3150, the Homeclans could be a military superpower again).
What you may underestimate is the level of automation the Clans`industry has achieved. This level must be very high and advanced, this will help them, either.