Diagram themes: adopt the DataJoint brand tier colors (retune _DIAGRAM_THEMES)

[dimitri-yatsenko]

#1534 modernized dj.Diagram rendering (light/dark/auto themes, entity clusters, adaptive SVG) but kept continuity-tuned tier hues. The intended tier palette adopts the DataJoint brand colors — the modernization was meant to carry the rebrand, not only the retune.

Target light-theme palette (fill / stroke / text):

Tier	Fill	Stroke	Text
Manual	#E8F0E9	#3E7A52	#28513A
Lookup	#F0F0F1	#808285	#5A5C5F
Imported	#E0F4FC	#00A0DF (DataJoint Blue)	#00537A
Computed	#FFEDE5	#FF5113 (DataJoint Orange)	#B23200
Part	#FFFFFF	#B9BBBE	#5A5C5F

Edges, cluster frames, and titles: Navy #171C39. Renamed-FK edges keep bronze #C77D3A (dark #D68C4A) — deliberately duller and darker than the computed orange so a renamed edge landing on a computed node never reads as the same signal (fallback if confused in review: bronze + dashed, never a new hue).

Scope:

• Retune _DIAGRAM_THEMES["light"] to the table above; derive the dark theme by the same rule as today (keep each tier's stroke hue, invert fills toward navy-tinted darks, brighten strokes/text to AA on #161A21).
• The adaptive mapping block derives from the palettes as it does now — no mechanism change.
• Text colors must hold WCAG AA against their fills (the values above were chosen for that; verify in tests, which is also where the earlier continuity values came out ahead — make the contrast check part of the theme test rather than hand-verification).
• Shapes, sizes, clusters, underlines, edge weights: unchanged — feat(#1532): modernize dj.Diagram rendering style #1534's structural work stands.

Continuity note: hue families are preserved (Manual green, Lookup grey, Imported blue, Computed warm), so tier recognition for long-time users survives; the change is anchoring Imported and Computed on the brand's blue and orange rather than generic blue/red.