Backyard Koi Pond with Rock Waterfall Build-Out

We want to turn an unused corner of our backyard into a proper koi pond with a rock waterfall, and we need someone who has actually built these before, not just watched a video on it. The footprint we're planning is roughly 11 by 8 feet with a deeper section at 34 inches so the fish have somewhere to shelter over winter and a shallower marginal shelf around the perimeter for plants. Excavation has to account for that depth variance, compacted subgrade, and a protective underlayment before the liner goes down — we've read too many stories about a rock puncturing a liner within the first season, so whatever underlayment or padding approach you use, we want it done right. Liner sizing needs to be calculated properly with enough overlap for the edges, not just eyeballed, since re-doing a poorly sized liner means draining the whole pond again. Filtration is the part we care about most because we're planning to stock actual koi, not just goldfish, and koi produce a lot of waste — we need a real biological filtration system, mechanical pre-filter plus a bio-filter with enough surface area for beneficial bacteria, sized to our water volume, not an undersized off-the-shelf unit. The waterfall itself should use real stacked rock, not a foam form, with a pump sized to move an appropriate turnover rate through the filter and back over the falls for aeration — koi need well-oxygenated water, especially in summer heat. Plumbing for the pump and the waterfall spillway needs to be planned before the rockwork goes in, including a bottom drain if that's part of your build style, so we're not fighting the liner and rocks afterward to fix a hose run. Edge design matters a lot for us — we've read that koi can jump and that poorly finished edges lead to fish getting scraped or even landscaping netting causing injuries, so we want koi-safe coping stones set with a slight overhang and no exposed liner edge anywhere visible. We'd like a rough timeline broken into excavation, liner and underlayment, plumbing and filtration install, waterfall rockwork, and final water fill with dechlorination and cycling before any fish go in — we understand the biological cycle takes real time and we're not going to rush that part. Please share examples of koi ponds you've built with photos of the excavation stage and the finished filtration setup, not just the pretty finished shot, since we want to see the parts that actually determine whether this works long term.