Honor per-strategy color when redacting PDFs and images

[jzonthemtn]

Implements the engine side of the redaction-policy schema change proposed in philterd/phisql#31: an optional color on each filter strategy that sets the PDF/image redaction bar color for spans that strategy redacts.

Blocked by philterd/phisql#31. Do not start until that RFC is accepted and the change lands in redaction-policy schema 1.2.0 (an additive, backward-compatible edit in place of the current schema version). The schema leads; Phileas follows, and the Phileas conformance test enforces that the engine implements everything the embedded schema declares.

Behavior to implement

• A strategy may carry an optional color. When rendering a redacted PDF or image, the bar over a span uses the color of the strategy that redacted it, if set; otherwise config.pdf.redactionColor; otherwise black. Exactly one strategy applies per span, so the color is unambiguous.
• Supported values: named colors black, white, red, orange, yellow, green, blue, gray, or a 6-digit hex string #RRGGBB. Any unrecognized or malformed value renders as black.
• The same set + fallback apply to the existing config.pdf.redactionColor and graphical.boundingBoxes[].color, which already share the COLORS table in PdfRedactor.
• No effect on text redaction: string output is unchanged.

Implementation notes (current code)

• src/main/java/ai/philterd/phileas/services/strategies/AbstractFilterStrategy.java holds the shared strategy fields (redactionFormat, maskCharacter, ...). Add color here so every strategy, including DateFilterStrategy, inherits it.
• src/main/java/ai/philterd/phileas/services/pdf/PdfRedactor.java:
  • The static COLORS map currently holds only white, black, red, yellow and does not parse hex, so blue, orange, green, gray, and any #RRGGBB currently fall back to black. Expand it to the 8 named colors and add 6-digit hex parsing, keeping the getOrDefault(..., black) fallback.
  • Fix the pre-existing scale bug in the yellow entry ({1, 1, 100 / 255F} mixes 0-1 and 0-255 component scales, while red uses {255, 0, 0}). Make the named-color RGB values use one consistent component scale.
  • Thread the redacting strategy's color onto each RedactedRectangle so the per-span bar (around lines 247-261) uses it instead of always config.pdf.getRedactionColor().
• Embed the updated 1.2.0 schema (now including color) and update the conformance test.

Acceptance criteria

• AbstractFilterStrategy exposes an optional color (getter/setter, @SerializedName("color")), inherited by all strategies including date.
• PdfRedactor draws each span's bar in its redacting strategy's color when set, else config.pdf.redactionColor, else black.
• COLORS supports all 8 named colors and 6-digit #RRGGBB hex; unrecognized or malformed values fall back to black.
• The yellow named-color RGB scale bug is fixed and all named colors use a consistent component scale.
• config.pdf.redactionColor and graphical.boundingBoxes[].color also resolve against the expanded set (shared table).
• Text-only redaction output is byte-identical with and without color set.
• Embedded redaction-policy schema is 1.2.0 (the revision that adds color) and the conformance test passes.
• PdfRedactorTest covers per-strategy color, the named palette, 6-digit hex, and black fallback for an unknown value.
• Documentation under docs/docs/ is updated for the new strategy property and the supported-color set.

[jzonthemtn]

The PhiSQL side is merged (philterd/phisql#32, closing RFC philterd/phisql#31): color is now an optional property on baseFilterStrategy and dateFilterStrategy in redaction-policy schema 1.2.0 (edited in place). This unblocks the engine work here.

For reference, the merged contract:

• Per span, the bar color resolves to the redacting strategy's color, then config.pdf.redactionColor, then black.
• Accepts a named color (black, white, red, orange, yellow, green, blue, gray) or a 6-digit #RRGGBB hex; an unrecognized or malformed value renders black.
• No effect on text redaction.

[jzonthemtn]

Downstream consumer: philterd/PhilterDesktop#36 exposes this per-strategy color in the desktop policy editor and depends on the engine rendering here (a PhilterDesktop build that bundles a Phileas version honoring color in PDF/image output).