Remove blessed postgres/s3/console code path from dc_bridge

[Minipada]

Parent

Follows #470 and #471 — nothing in the repo may still reference the blessed
postgres/s3/console param form before this lands, or CI breaks.

What to build

The C++ param declaration, TOML templating, and validation logic for the postgres,
s3, and console blessed destination types is deleted from dc_bridge. The Bridge's
blessed set shrinks to file and vector only; any destinations entry with
type: postgres|s3|console is now handled purely as an unrecognized type (i.e. must go
through custom_config_files passthrough — no special-cased error message for these
three beyond the Bridge's normal unknown-type rejection).

Acceptance criteria

• postgres/s3/console param declarations, templating, and their dedicated
  validation branches removed from dc_bridge (render.cpp, bridge_node.cpp)
• Their unit/render tests removed or repurposed to cover passthrough instead
• destinations.md's blessed-set table and Bridge parameter docs updated to show
  only file and vector as blessed
• future_work.md updated if it references the old 5-type blessed set
• colcon test passes; no remaining reference to the removed code path anywhere in
  the repo (docs, demos, deploy params were already migrated in Migrate demos, deploy params, and docs off blessed postgres/s3/console #471)

Blocked by

• Migrate demos, deploy params, and docs off blessed postgres/s3/console #471 — all consumers must be migrated to passthrough before the code path is deleted