Add Pheenix galvanics flyers and Sibert stamper prep specs

docs/equipment/pheenix-alpha/: the four Pheenix Alpha electroforming flyers
(2024: PASU silvering, PPPU pre-plating, PDPU dual-cell plating, PMPB
passivation bench), renamed from their download hashes.
docs/equipment/sibert/: the VSP, VSF and VSC technical specifications
(2021), plus Sibert's 2008-09 optical-disc SPS literature and the 2008
Blu-ray stamper characteristics paper in sps-optical-disc-2009/. Two
byte-identical duplicates in the download were dropped.

New docs/equipment/galvanics.md, the metal-path counterpart to
pressing-line.md: datasheet tables for both ranges and what they change.
Pheenix is a second turnkey galvanics vendor next to Digital Matrix and
can quote lacquer-to-record as one vendor; neither range includes water
treatment. Utilities from the sheets (~27 kVA connected per line, DI water,
12-20 C cooling water, extraction sizes), ~5.6 m2 of footprint, and a cell
count estimate (one PDPU at the low end, two at the high end). The Sibert
machines are single-phase, 200/250/600 kg on castors, centre manually and
list no data interface; the VSC locates on the punched hole; the finisher's
water carries nickel. Weights, cycle times, prices and mould fit are listed
as quote questions.

Backlinks and small updates: README (bullet, layout tree, vendor list),
roadmap items 6 and 23, vendor landscape, supplier map, exhibitor briefing
(on-file notes, Sibert three-phase question answered), digital factory
(Pheenix PLC data, Sibert data question, RFQ clause 5), quality automation
(hardness on the centre slug, BD paper as the acceptance-spec model),
sustainability (finisher water), total investment block label (numbers
unchanged), scale (galvanics feeder note), crane weight table, process
flow, pressing-line stamper-fit question, plant page detail lines.

docs/process-flow.md

@@ -4,7 +4,9 @@ The complete chain with every check and approval gate. Three gates involve
 the artist or label directly (marked as approval gates); everything else is
 internal QC. Every step writes to the [traceability
 database](traceability.md); the instruments behind the checks are specified
-in [quality automation](quality-automation.md).
+in [quality automation](quality-automation.md), the machines for stages 4
+to 6 in [galvanics and stamper prep](equipment/galvanics.md) and the
+[pressing line](equipment/pressing-line.md).
 
 A printable diagram of this flow lives alongside this document:
 [process-flow.drawio](process-flow.drawio) (editable),